COMMUNICATION SYSTEM, RELAY DEVICE, AND COMMUNICATION METHOD

Abstract

To provide a communication system or the like that improves communication reliability and communication efficiency in a redundancy mode communication system connecting in a MC-LAG mode and a linear protection mode.SOLUTION: A communication system connects in a linear protection mode between a first relaying device and a third relaying device, between the first relaying device and a second relaying device, between the second relaying device and a fourth relaying device, and between the third relaying device and the fourth relaying device. The first relaying device establishes connection to a first communication device that connects in a MC-LAG mode as a starting end point of a linear protection mode logical path. The third relaying device establishes connection of a logical path in a first path as a first terminal point of the logical path for the starting end point, and communicates with a second communication device connecting in the MC-LAG mode. The fourth relaying device establishes connection of a logical path in a second path as a second terminal point of the logical path for the starting end point, and communicates with the second communication device connecting in the MC-LAG mode.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a communication system, a relay device, and a communication method. [Background technology]

[0002] In recent years, MC-LAG (Multi-Chassis Link Aggregation) has become known as an extension technology of LAG (Link Aggregation). MC-LAG is a technology that extends LAG between adjacent transmission devices and constructs LAG by making multiple transmission devices appear logically as a single transmission device. For example, MC-LAG has a redundant configuration of ACT / STBY, where one of two routes is ACT (Active) and the other is STBY (Standby) and used as a backup.

[0003] Linear protection is also known as a communication system with a redundant configuration. Linear protection is a technology standardized by ITU-T, such as Ethernet Linier Protection (ELP) G.8031 and Linear protection switching for MPLS Transport Profile G.8131. In linear protection, for example, communication between transmission devices is set to two routes, a work route and a protection route, and each route is section-monitored by an OAM (Operation, Administration, and Maintenance) signal. In linear protection, communication is normally performed via the work route, and when a switching cause such as a fault occurs as a result of monitoring the OAM signal, communication is switched from the work route to the protection route. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-88735 A Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, in recent years, when connecting a communication device to an opposing communication device using MC-LAG and linear protection, there is a demand for a redundant communication system that has high communication reliability and good communication efficiency.

[0006] In one aspect, an object of the present invention is to provide a communication system etc. that improves communication reliability and communication efficiency in a redundant communication system connected by the MC-LAG method and the linear protection method. [Means for solving the problem]

[0007] In one embodiment, the communication system includes a first relay device and a second relay device that are connected to a first communication device in a first MC-LAG method, and a third relay device and a fourth relay device that are connected to the second communication device in a second MC-LAG method. The communication system connects the first relay device and the third relay device, the first relay device and the second relay device, the second relay device and the fourth relay device, and the third relay device and the fourth relay device in a linear protection method. The first relay device establishes a connection with the first communication device as a starting point of a logical path of the linear protection method. The third relay device establishes a connection of a logical path in a first route of the linear protection method as a first ending point of the logical path for the starting point, and executes communication with the second communication device. The fourth relay device establishes a connection of a logical path on a second route of the linear protection method as a second termination point of the logical path with respect to the starting point, and executes communication with the second communication device. Effect of the Invention

[0008] One aspect is to improve communication reliability and efficiency in a redundant communication system connected using the MC-LAG method and the linear protection method. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram illustrating an example of a communication system (MC-LAG ACT / STBY) according to a first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram illustrating an example of the configuration of the first relay device. [Diagram 3] FIG. 3 is an explanatory diagram showing an example of a setting state of start and end points of a logical path in a linear protection section. [Figure 4] FIG. 4 is an explanatory diagram showing an example of OAM signal transparent forwarding at a termination point of a logical path in a linear protection section. [Diagram 5] FIG. 5 is an explanatory diagram illustrating an example of a default route of a logical path in a linear protection section. [Figure 6] FIG. 6 is an explanatory diagram illustrating an example of the switching determination table of the first relay device. [Figure 7] FIG. 7 is an explanatory diagram illustrating an example of a provisioning model of a communication system. [Figure 8] FIG. 8 is an explanatory diagram showing an example of a provisioning model and a configuration table of the first relay device. [Figure 9] FIG. 9 is an explanatory diagram showing an example of a provisioning model and a configuration table of the second relay device. [Figure 10] FIG. 10 is an explanatory diagram showing an example of a provisioning model and a configuration table of the third relay device. [Figure 11] FIG. 11 is an explanatory diagram showing an example of a provisioning model and a configuration table of the fourth relay device. [Figure 12] FIG. 12 is an explanatory diagram illustrating an example of a communication system in an initial state. [Figure 13] FIG. 13 is an explanatory diagram illustrating an example of a communication system when a failure occurs in the third relay device. [Figure 14] FIG. 14 is an explanatory diagram showing an example of a communication system when a default route is set. [Figure 15]FIG. 15 is an explanatory diagram illustrating an example of a communication system when the third relay device recovers from a failure. [Figure 16A] FIG. 16A is an explanatory diagram showing an example of a communication system when the third relay device recovers from a failure. [Figure 16B] FIG. 16B is an explanatory diagram illustrating an example of a communication system when the Work route is switched back when the third relay device recovers from a failure. [Figure 17A] FIG. 17A is an explanatory diagram illustrating an example of a communication system (MC-LAG ACT / ACT) according to a second embodiment. [Figure 17B] FIG. 17B is an explanatory diagram showing an example of a provisioning model of a communication system. [Figure 18] FIG. 18 is an explanatory diagram illustrating an example of a communication system of a comparative example. [Figure 19] FIG. 19 is an explanatory diagram showing an example of the operation of the communication system at the time of link switching in the eleventh MC-LAG of the comparative example. [Figure 20] FIG. 20 is an explanatory diagram showing an example of the operation of the communication system when a failure occurs on the Work path between the eleventh relay device and the thirteenth relay device of the comparative example. [Figure 21] FIG. 21 is an explanatory diagram showing an example of the operation of the communication system at the time of link switching in the twelfth MC-LAG of the comparative example. [Figure 22] FIG. 22 is an explanatory diagram showing an example of a loopback operation of MC-LAG and linear protection between the thirteenth relay device and the fourteenth relay device in the comparative example. [Figure 23] FIG. 23 is an explanatory diagram showing an example of a problem that occurs when the starting point:terminating point of a logical path in a linear protection section of a comparative example is 1:1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Comparative Example> Fig. 18 is an explanatory diagram showing an example of a communication system 100 of a comparative example. The communication system 100 shown in Fig. 18 has a configuration in which an eleventh communication device 400A and a twelfth communication device 400B on the opposite side are connected by an eleventh MC-LAG section 200A, a twelfth MC-LAG section 200B, and a linear protection section 300.

[0011] The eleventh MC-LAG section 200A connects the links between the eleventh communication device 400A and the eleventh relay device 500A and between the eleventh communication device 400A and the twelfth relay device 500B using the MC-LAG (Multi-Chassis Link Aggregation) method. The eleventh MC-LAG section 200A connects the eleventh relay device 500A and the twelfth relay device 500B using an IPL (Intra-Portal Link). The eleventh relay device 500A and the twelfth relay device 500B exchange synchronization information using the IPL.

[0012] The twelfth MC-LAG section 200B connects the links between the twelfth communication device 400B and the thirteenth relay device 500C and between the twelfth communication device 400B and the fourteenth relay device 500D in the MC-LAG system. The twelfth MC-LAG section 200B connects the thirteenth relay device 500C and the fourteenth relay device 500D by an IPL (Intra-Portal Link). Synchronization information is exchanged between the thirteenth relay device 500C and the fourteenth relay device 500D by the IPL.

[0013] The linear protection section 300 connects between an eleventh relay device 500A and a twelfth relay device 500B that are paired in the eleventh MC-LAG section 200A and a thirteenth relay device 500C and a fourteenth relay device 500D that are paired in the twelfth MC-LAG section 200B in a linear protection method. Note that, for example, G.8031 is adopted as the linear protection method.

[0014] In the eleventh MC-LAG section 200A, for example, the link between the eleventh communication device 400A and the eleventh relay device 500A is set to ACT (Active), and the link between the eleventh communication device 400A and the twelfth relay device 500B is set to STBY (Standby). Furthermore, in the twelfth MC-LAG section 200B, for example, the link between the twelfth communication device 400B and the thirteenth relay device 500C is set to ACT, and the link between the twelfth communication device 400B and the fourteenth relay device 500D is set to STBY.

[0015] In the linear protection section 300, the relationship between the start point and the end point of each logical path is 1:1. For example, the eleventh relay device 500A is the start point P101 of the first logical path, and the thirteenth relay device 500C is the end point P111 of the start point P101. The eleventh relay device 500A sets, for example, the route between the eleventh relay device 500A and the thirteenth relay device 500C as the Work route of the first logical path. Furthermore, the eleventh relay device 500A sets, for example, the route from the twelfth relay device 500B to the fourteenth relay device 500D to the thirteenth relay device 500C as the Protection route of the first logical path.

[0016] Also, for example, the twelfth relay device 500B is the starting point P102 of the second logical path, and the thirteenth relay device 500C is the ending point P122 of the starting point P102. The twelfth relay device 500B sets, for example, the route via the eleventh relay device 500A → the thirteenth relay device 500C → the fourteenth relay device 500D as the Work route of the second logical path. The twelfth relay device 500B sets, for example, the route between the twelfth relay device 500B and the fourteenth relay device 500D as the Protection route of the second logical path.

[0017] FIG. 19 is an explanatory diagram showing an example of the operation of the communication system 100 at the time of link switching in the eleventh MC-LAG section 200A of the comparative example. In FIG. 19, when the link between the eleventh communication device 400A and the eleventh relay device 500A is switched from ACT to STBY, the link between the eleventh communication device 400A and the twelfth relay device 500B is switched from STBY to ACT. At this time, in the linear protection section 300, the starting point P101 of the first logical path is switched to the starting point P102 of the second logical path, and the Work route of the second logical path from the twelfth relay device 500B to the eleventh relay device 500A to the thirteenth relay device 500C is switched. In other words, the operation of switching the link in the eleventh MC-LAG section 200A of the comparative example is a mechanism that involves the operation of changing the transmitting end (starting point) in the linear protection section 300.

[0018] FIG. 20 is an explanatory diagram showing an example of the operation of the communication system 100 when a failure occurs on the Work path between the eleventh relay device 500A and the thirteenth relay device 500C in the comparative example. In FIG. 20, when a failure occurs on the Work path between the eleventh relay device 500A and the thirteenth relay device 500C, in the linear protection section 300, the first logical path is switched from the Work path to the Protection path, thereby switching to a path of the eleventh relay device 500A → the twelfth relay device 500B → the fourteenth relay device 500D → the thirteenth relay device 500C. However, in the eleventh MC-LAG section 200A, the link between the eleventh communication device 400A and the eleventh relay device 500A remains in ACT. In addition, in the twelfth MC-LAG section 200B, the link between the twelfth communication device 400B and the thirteenth relay device 500C also remains in ACT. In other words, the switching operation of the linear protection section 300 in the comparative example is not coordinated with the link switching operation of the eleventh MC-LAG section 200A and the twelfth MC-LAG section 200B.

[0019] 21 is an explanatory diagram showing an example of the operation of the communication system 100 when switching the link of the LAG in the 12th MC-LAG section 200B of the comparative example. In FIG. 21, when switching of the link between the 12th communication device 400B and the 13th relay device 500C from ACT to STBY occurs, the link between the 12th communication device 400B and the 14th relay device 500D is switched from STBY to ACT. However, the operation of switching the link in the 12th MC-LAG section 200B of the comparative example is not linked to the operation of changing the termination point in the linear protection section 300.

[0020] 22 is an explanatory diagram showing an example of a return operation of MC-LAG and linear protection between the 13th relay device 500C and the 14th relay device 500D of the comparative example. In the 11th MC-LAG section 200A, the link between the 11th communication device 400A and the 12th relay device 500B may be ACT, and in the 12th MC-LAG section 200B, the link between the 13th relay device 500C and the 12th communication device 400B may be ACT. In this case, in the linear protection section 300, the second logical path of the 12th relay device 500B → the 11th relay device 500A → the 13th relay device 500C → the 14th relay device 500D may be set as a Work route. Furthermore, the 14th relay device 500D may have a termination point of the logical path of the linear protection section 300 set, but the link between the 12th communication device 400B of the 12th MC-LAG section 200B and the 12th communication device 400B may be set to STBY. That is, the termination point of the logical path of the linear protection section 300 and the ACT port of the 12th MC-LAG section 200B may not exist in the same relay device. Therefore, the 11th communication device 400A transmits a main signal to the 12th communication device 400B via the 12th relay device 500B → the 11th relay device 500A → the 13th relay device 500C → the Work route of the linear protection section 300 of the 14th relay device 500D → the IPL between the 14th relay device 500D and the 13th relay device 500C in the 12th MC-LAG section 200B.

[0021] However, return communication occurs between paired relay devices in the linear protection section 300, for example, between a path from the thirteenth relay device 500C to the fourteenth relay device 500D and an IPL path from the fourteenth relay device 500D to the thirteenth relay device 500C in the twelfth MC-LAG section 200B. As a result, the flow rate of the main signal increases in the return communication between the thirteenth relay device 500C and the fourteenth relay device 500D, and communication efficiency decreases in the communication system 100 of the comparative example.

[0022] FIG. 23 is an explanatory diagram showing an example of a problem when the ratio of the start point:end point of the logical path in the linear protection section 300 of the comparative example is 1:1. In FIG. 23, the linear protection section 300 of the comparative example has a mechanism in which the start point and end point of each logical path are 1:1. For example, when the start point P101 of the first logical path is in the eleventh relay device 500A, the end point P111 for the start point P101 of the first logical path is in the thirteenth relay device 500C. In this case, if the thirteenth relay device 500C where the end point P111 of the first logical path in the linear protection section 300 is located breaks down, the first logical path is interrupted. As a result, the communication reliability is reduced in the communication system 100 of the comparative example.

[0023] Therefore, in order to solve the problem of the decrease in communication efficiency shown in Fig. 22 and the decrease in communication reliability shown in Fig. 23, a communication system 1 according to the present embodiment is provided. Hereinafter, an embodiment of the communication system 1 disclosed in the present application will be described in detail with reference to the drawings. Note that the disclosed technology is not limited to the embodiment. Also, the embodiments shown below may be appropriately combined as long as no contradiction occurs. EXAMPLES

[0024] Fig. 1 is an explanatory diagram showing an example of a communication system 1 (MC-LAG ACT / STBY) according to a first embodiment. The communication system 1 shown in Fig. 1 has a configuration in which a first MC-LAG section 2A, a second MC-LAG section 2B, and a linear protection section 3 are arranged between a first communication device 4A and a second communication device 4B.

[0025] The first MC-LAG section 2A is a redundant client section that connects the first communication device 4A and the first relay device 5A and the first communication device 4A and the second relay device 5B using the MC-LAG (Multi-Chassis Link Aggregation) method. The first MC-LAG section 2A has an ACT / STBY configuration in which one link is used for operation and the other link is used as a backup. The first MC-LAG section 2A connects the first relay device 5A and the second relay device 5B using an IPL (Intra-Portal Link). Synchronization information is exchanged between the first relay device 5A and the second relay device 5B using the IPL.

[0026] The second MC-LAG section 2B is a client section with a redundant configuration that connects the second communication device 4B and the third relay device 5C and the second communication device 4B and the fourth relay device 5D using the MC-LAG method. The second MC-LAG section 2B has an ACT / STBY configuration in which one link is used for operation and the other link is used as a backup. The second MC-LAG section 2B connects the third relay device 5C and the fourth relay device 5D using IPL. Synchronization information is exchanged between the third relay device 5C and the fourth relay device 5D using IPL.

[0027] The linear protection section 3 connects the first relay device 5A and the second relay device 5B in a pair configuration in the first MC-LAG section 2A with the third relay device 5C and the fourth relay device 5D in a pair configuration in the second MC-LAG section 2B using a linear protection method. Note that, for example, G.8031 is adopted as the linear protection method. The route switching time of the work route and the protection route, etc. for each logical path in the linear protection section 3 is, for example, within 50 ms.

[0028] In the first MC-LAG section 2A, for example, the link between the first communication device 4A and the first relay device 5A is set to ACT, and the link between the first communication device 4A and the second relay device 5B is set to STBY. ACT is a state in which the link (connection) between the devices is activated, and STBY is a state in which the link (connection) between the devices is deactivated. The link switching time of the first MC-LAG section 2A is, for example, within one second. Furthermore, in the second MC-LAG section 2B, for example, the link between the second communication device 4B and the third relay device 5C is set to ACT, and the link between the second communication device 4B and the fourth relay device 5D is set to STBY. The link switching time of the second MC-LAG section 2B is, for example, within one second.

[0029] In the communication system 1, it is desirable that the redundancy scheme for each of the first MC-LAG section 2A, the linear protection section 3, and the second MC-LAG section 2B be performed independently.

[0030] 2 is an explanatory diagram showing an example of the configuration of the first relay device 5A. For convenience of explanation, the first relay device 5A is illustrated and explained, but since the second relay device 5B, the third relay device 5C, and the fourth relay device 5D have substantially the same configuration, the same components are given the same reference numerals, and explanations of the overlapping configurations and operations are omitted.

[0031] The first relay device 5A has a route SW11, a main signal communication unit 12, an OAM communication unit 13, a MEP monitoring unit 14, a memory unit 15, and a processor 16. The route SW11 switches the route of the logical path in the linear protection section 3. The main signal communication unit 12 is a communication IF that transmits and receives a main signal through the logical path. The OAM communication unit 13 is a MEP (Maintenance End Point) that transmits and receives an OAM signal through the logical path. The MEP monitoring unit 14 monitors the MEP that detects the route state of the logical path based on the OAM signal. The processor 16 controls the entire first relay device 5A.

[0032] The storage unit 15 has a configuration table 15A and an MC-LAG table 15B. The configuration table 15A is a table for managing the configuration in the linear protection section 3. The configuration table 15A has a linear protection table 21, an FP table 22, an MEP table 23, and a switching determination table 24. The linear protection table 21 is a table for storing, for example, an FP (Flow Point) which is a logical port of the Work path, an FP of the Protection path, and an FP of the default path for each logical path such as a VLAN.

[0033] The FP table 22 stores, for each FP, a domain ID that identifies the VLAN to which the FP is addressed, and a VLAN ID that identifies the VLAN. st Tag ID and VLAN 2 to identify the VLAN nd This is a table that stores VLAN IDs in association with each other. st The Tag ID is the CVID of the client side for the DropFP VLAN on the MC-LAG section side, whereas the Tag ID is the VID that identifies the logical path of the linear protection method for the FP VLAN on the linear protection section 3 side. nd Tag ID is VLAN 1 st This ID is used when the Tag ID is a VID of the linear protection method, and is an ID that inherits the CVID on the client side. The MEP table 23 is a table that stores an FP that indicates the location of the MEP. The switching decision table 24 is a table that stores a route to be used for a logical path corresponding to the monitoring result of the Work route and the monitoring result of the Protection route. The MC-LAG table 15B is a table that stores, for example, the STBY / ACT setting of the link of the first MC-LAG section 2A.

[0034] The processor 16 has a setting unit 16A, a detection unit 16B, and a switching setting unit 16C. The setting unit 16A sets a configuration in a configuration table 15A that manages, for example, a start point, a termination point, and an FP in response to a setting operation. The detection unit 16B detects the state on the route in the linear protection section 3 and detects the state on the first MC-LAG section 2A based on the monitoring result of the MEP monitoring unit 14. The switching setting unit 16C controls a route SW11 that switches the route on the linear protection section 3. Furthermore, the switching setting unit 16C switches, for example, a link with the first communication device 4A in the first MC-LAG section 2A and an IPL with the second relay device 5B in the first MC-LAG section 2A.

[0035] 3 is an explanatory diagram showing an example of a setting state of a start point and a termination point of a logical path in a linear protection section 3. In the linear protection section 3, the start point of the logical path is set to a first relay device 5A and a second relay device 5B in a pair configuration in a first MC-LAG section 2A. A first start point P1 of the logical path is set to the first relay device 5A in the first MC-LAG section 2A. The first relay device 5A establishes a connection with a first communication device 4A in the first MC-LAG section 2A as the first start point P1. In addition, a second start point P2 of the logical path is also set to a second relay device 5B in the first MC-LAG section 2A. The second relay device 5B establishes a connection with the first communication device 4A in the first MC-LAG section 2A as the second start point P2. For ease of explanation, the logical path from the first starting point P1 will be referred to as the first logical path, and the logical path from the second starting point P2 will be referred to as the second logical path. The starting points of the linear protection section 3 are set to the first relay device 5A and the second relay device 5B that are paired in the first MC-LAG section 2A. As a result, the starting points can be switched in response to link switching in the first MC-LAG section 2A.

[0036] In the linear protection section 3, the termination points for the starting point of the logical path are set to the third relay device 5C and the fourth relay device 5D in a pair configuration in the second MC-LAG section 2B. For example, the termination points for the first starting point P1 of the first logical path are set to the termination point P11 in the third relay device 5C and the termination point P12 in the fourth relay device 5D in the second MC-LAG section 2B. The third relay device 5C establishes a connection of a route of the linear protection method with the termination point P11 of the first logical path for the first starting point P1. Furthermore, the fourth relay device 5D establishes a connection of a route of the linear protection method with the termination point P12 of the first logical path for the first starting point P1.

[0037] Furthermore, the termination points for the second starting point P2 of the second logical path are set to termination point P21 in the third relay device 5C and termination point P22 in the fourth relay device 5D in the second MC-LAG section 2B. The third relay device 5C establishes a linear protection system route connection with the termination point P21 of the second logical path for the second starting point P2. Furthermore, the fourth relay device 5D establishes a linear protection system route connection with the termination point P22 of the second logical path for the second starting point P2. Since the termination points for the starting point of the linear protection section 3 are set to the third relay device 5C and the fourth relay device 5D in the pair configuration, it is possible to provide relief in the event of an equipment failure, and it is possible to prevent the main signal from traveling back and forth between the third relay device 5C and the fourth relay device 5D in the pair configuration.

[0038] FIG. 4 is an explanatory diagram showing an example of OAM signal transparent forwarding at the termination point of the logical path in the linear protection section 3. The first logical path in the linear protection section 3 has a work route of the first logical path between the first relay device 5A and the third relay device 5C, and a protection route of the first logical path via the first relay device 5A → the second relay device 5B → the fourth relay device 5D. MEP1 in the first relay device 5A and MEP1 in the third relay device 5C monitor the OAM signal passing through the work route of the first logical path, and monitor the route status of the section of the work route of the first logical path based on the monitoring result. MEP2 in the first relay device 5A and MEP2 in the third relay device 5C monitor the OAM signal passing through the protection route of the first logical path, and monitor the route status of the section of the protection route of the first logical path based on the monitoring result. The termination point P12 in the fourth relay device 5D of the Protection route of the first logical path terminates the main signal of the first logical path and transfers the OAM signal of the first logical path to the MEP2 in the third relay device 5C. That is, the fourth relay device 5D establishes a connection of the first logical path in the Protection route, for example, executes communication of the main signal with the second communication device 4B, and executes communication of the OAM signal with the third relay device 5C. As a result, the MEP2 in the first relay device 5A and the MEP2 in the third relay device 5C monitor the OAM signal flowing on the route from the second relay device 5B to the termination point P12 of the fourth relay device 5D to the third relay device 5C. Then, MEP2 in the first relay device 5A and MEP2 in the third relay device 5C can monitor the route status of the default route of the main signal from the first relay device 5A to the second relay device 5B to the termination point P12 of the fourth relay device 5D, as described below.

[0039] The second logical path of the linear protection section 3 has a work route via the second relay device 5B → the first relay device 5A → the third relay device 5C, and a protection route via the second relay device 5B → the fourth relay device 5D. The MEP4 in the first relay device 5A and the MEP4 in the third relay device 5C monitor the OAM signal passing through the work route of the second logical path, and monitor the route status of the section of the work route of the second logical path based on the monitoring result. The MEP3 in the second relay device 5B and the MEP3 in the fourth relay device 5D monitor the OAM signal passing through the protection route of the second logical path, and monitor the route status of the protection route of the second logical path based on the monitoring result. The termination point P21 in the third relay device 5C on the Work route of the second logical path terminates the main signal of the second logical path and transfers the OAM signal of the second logical path to the MEP4 in the fourth relay device 5D. That is, the third relay device 5C establishes a connection of the second logical path on the Work route, for example, and executes communication of the main signal with the second communication device 4B and communication of the OAM signal with the fourth relay device 5D. As a result, the MEP4 in the second relay device 5B and the MEP4 in the fourth relay device 5D monitor the OAM signal flowing through the route from the second relay device 5B to the first relay device 5A to the termination point P21 of the third relay device 5C to the fourth relay device 5D. Then, MEP4 in the second relay device 5B and MEP4 in the fourth relay device 5D can monitor the route status of the default route of the main signal from the second relay device 5B to the first relay device 5A to the termination point P21 of the third relay device 5C, as described below.

[0040] FIG. 5 is an explanatory diagram showing an example of a default route of a logical path in the linear protection section 3. In FIG. 5, among the routes from the starting point of the logical path in the linear protection section 3 to the two ending points, a route that uses a route passing between the first relay device 5A and the second relay device 5B in a pair configuration is set as the default route. For example, the default route of the first logical path is a route from the first starting point P1 of the first relay device 5A in the first MC-LAG section 2A through the second relay device 5B to the fourth relay device 5D at the ending point P12 of the first logical path. For example, the default route of the second logical path is a route from the second starting point P2 of the second relay device 5B in the first MC-LAG section 2A through the first relay device 5A to the third relay device 5C at the ending point P21 of the second logical path. In the first relay device 5A and the second relay device 5B, when a switching event, for example, a failure in both the Work path and the Protection path, is detected, a default path is set.

[0041] 6 is an explanatory diagram showing an example of the switching decision table 24 of the first relay device 5A. The switching decision table 24 is a table that stores the monitoring result of the Work path, the monitoring result of the Protection path, and the path to be used for the logical path in association with each other. The monitoring result of the Work path is the monitoring result of the OAM signal monitored by MEP1. The monitoring result of the Protection path is also the monitoring result of the OAM signal monitored by MEP2. The switching setting unit 16C in the processor 16 in the first relay device 5A refers to the switching decision table 24, and when the monitoring result of the Work path is normal, the switching setting unit 16C uses the Work path as the path to be used for the first logical path. When the monitoring result of the Work path is abnormal and the monitoring result of the Protection path is normal, the switching setting unit 16C refers to the switching decision table 24, and when the monitoring result of the Work path is abnormal and the monitoring result of the Protection path is normal, the switching setting unit 16C uses the Protection path as the path to be used for the first logical path. The switching setting unit 16C refers to the switching determination table 24, and when the monitoring result of the Work path and the monitoring result of the Protection path are abnormal, that is, when there is a failure in both systems, uses the default path as the path to be used for the first logical path.

[0042] 7 is an explanatory diagram showing an example of a provisioning model of the communication system 1. For convenience of explanation, the VLAN of DropFP1 on the MC-LAG section side is set to "1" as the CVID on the client side. The VID of the VLAN of the first logical path of the FP on the linear protection section 3 side is set to "11". Furthermore, the VID of the VLAN of the second logical path of the FP on the linear protection section 3 side is set to "12". VLAN 1 st For the VLAN of DropFP on the MC-LAG section, the Tag ID is the CVID on the client side. st In the case of a VLAN of an FP on the linear protection section 3 side, the tag ID is a VID that identifies the logical path of the linear protection method. nd Tag ID is VLAN 1 st This is used when the tag ID is a VID of the linear protection method, and is the ID inherited from the CVID on the client side.

[0043] The first relay device 5A has DropFP1, FP111, FP112, FP121, and FP122. DropFP1 of the first relay device 5A is an FP that connects to the LAG of the first communication device 4A in the first MC-LAG section 2A. FP111 of the first relay device 5A is an FP that connects to the FP111 of the second relay device 5B and connects to the Work path of VLAN11 of the first logical path. FP112 of the first relay device 5A is an FP that connects to the FP112 of the second relay device 5B and connects to the Protection path of VLAN11 of the first logical path. FP122 of the first relay device 5A is an FP that connects to the FP122 in the second relay device 5B and connects to the Work path of VLAN12, which is the second logical path. The FP 121 of the first relay device 5A is an FP connected to the Work path of VLAN 12, which is the second logical path, and is connected to the FP 121 of the third relay device 5C.

[0044] The second relay device 5B has DropFP1, FP111, FP112, FP121, and FP122. DropFP1 of the second relay device 5B is an FP that connects to the LAG of the first communication device 4A in the first MC-LAG section 2A. FP111 of the second relay device 5B is an FP that connects to the FP111 of the fourth relay device 5D and connects to the Protection path of VLAN11 of the first logical path. FP112 of the second relay device 5B is an FP that connects to the FP112 of the first relay device 5A and connects to the Protection path of VLAN11 of the first logical path. FP122 of the second relay device 5B is an FP that connects to the FP122 in the first relay device 5A and connects to the Work path of VLAN12, which is the second logical path. The FP 121 of the second relay device 5B is an FP connected to the Protection path of the VLAN 12, which is the second logical path, and is connected to the FP 121 of the fourth relay device 5D.

[0045] The third relay device 5C has DropFP1, FP111, FP121, and a virtual LAG. DropFP1 of the third relay device 5C is an FP that connects to the LAG of the second communication device 4B in the second MC-LAG section 2B. FP111 of the third relay device 5C is an FP that connects to the FP111 of the first relay device 5A and connects to the Work path of VLAN11 of the first logical path. FP121 of the third relay device 5C is an FP that connects to the FP121 of the first relay device 5A and connects to the Work path of VLAN12, which is the second logical path. The virtual LAG is an FP that connects to the fourth relay device 5D in the second MC-LAG section 2B and the IPL of VLAN1, and also connects to DropFP1.

[0046] The fourth relay device 5D has DropFP1, FP111, FP121, and a virtual LAG. DropFP1 of the fourth relay device 5D is an FP that connects to the LAG of the second communication device 4B in the second MC-LAG section 2B. FP111 of the fourth relay device 5D is an FP that connects to the FP111 of the second relay device 5B and connects to the Protection path of VLAN11 of the first logical path. FP121 of the fourth relay device 5D is an FP that connects to the FP121 of the second relay device 5B and connects to the Protection path of VLAN12, which is the second logical path. The virtual LAG is an FP that connects to the third relay device 5C in the second MC-LAG section 2B and the IPL of VLAN1, and also connects to DropFP1.

[0047] FIG. 8 is an explanatory diagram showing an example of a provisioning model and a configuration table 15A of the first relay device 5A. For convenience of explanation, only the information of the FP related to the first logical path (VID "11") will be explained, and the explanation of the information of the FP related to the second logical path (VID "12") will be omitted. The first relay device 5A has DropFP1, FP111, and FP112. The first relay device 5A has a first starting point P1 of the first logical path in the linear protection section 3. DropFP1 of the first relay device 5A is an FP that connects to the LAG of the first communication device 4A in the first MC-LAG section 2A. FP111 of the first relay device 5A is an FP that connects to the Work route of the first logical path between the first relay device 5A and the third relay device 5C. The MEP1 arranged at FP111 monitors the OAM signal of the Work route of the first logical path. The FP 112 of the first relay device 5A is an FP connected to the protection route of the first logical path between the first relay device 5A and the second relay device 5B. The MEP 2 arranged at the FP 112 monitors the OAM signal of the protection route of the first logical path.

[0048] The linear protection table 21 in the first relay device 5A stores, for each logical path (domain-id), an FP (Work-fp) of the work path, an FP (protection-fp) of the protection path, and an FP (default-fp) of the default path. The linear protection table 21 stores domain-id "1" for identifying the first logical path, "111" of FP111 as an FP (Work-fp) of the work path of the first logical path, "112" of FP112 as an FP (protection-fp) of the protection path of the first logical path, and "112" of FP112 as an FP (default-fp) of the default path of the first logical path. The FP table 22 stores a number for identifying an FP to be used for each logical path. For example, the FP table 22 stores “1” of DropFP1, “111” of FP111, and “112” of FP112 as FPs used by the first logical path with a domain ID of “1”. st Tag ID is CVID “1”, VLAN 1 for FP111 and FP112 st The VID “11” is stored as the Tag ID. Furthermore, the FP table 22 stores the VLAN 2 nd Store CVID “1” as the Tag ID.

[0049] The MEP table 23 stores a number identifying an MEP (MEP-ID), a number identifying an FP in which the MEP is located (interface), and a number identifying an opposing MEP (peer MEP-ID). The MEP table 23 stores "1" for MEP1 as the MEP-ID, "111" for FP111 as the interface, and "1" for opposing MEP1 as the peer MEP-ID. The MEP table 23 stores "2" for MEP2 as the MEP-ID, "112" for FP112 as the interface, and "2" for opposing MEP2 as the peer MEP-ID.

[0050] FIG. 9 is an explanatory diagram showing an example of the provisioning model and the configuration table 15A of the second relay device 5B. For convenience of explanation, only the information of the FP related to the first logical path will be explained, and the explanation of the information of the FP related to the second logical path will be omitted. The second relay device 5B has FP111 and FP112. The second relay device 5B has a protection path of the first logical path in the linear protection section 3. The FP112 of the second relay device 5B is an FP that connects to the protection path of the first logical path between the first relay device 5A. The FP111 of the second relay device 5B is an FP that connects to the protection path of the first logical path between the fourth relay device 5D. The FP table 22 of the second relay device 5B stores FPs "111" and "112" used by the first logical path. The FP table 22 stores VLAN 1 of FP111 and FP112. st The VID “11” is stored as the Tag ID. Furthermore, the FP table 22 stores the VLAN 2 nd Store CVID “1” as the Tag ID.

[0051] FIG. 10 is an explanatory diagram showing an example of the provisioning model and the configuration table 15A of the third relay device 5C. For convenience of explanation, only the information of the FP related to the first logical path will be explained, and the explanation of the information of the FP related to the second logical path will be omitted. The third relay device 5C has FP111, FP112, DropFP1, and a virtual LAG. The third relay device 5C has a work route of the first logical path in the linear protection section 3. The FP111 of the third relay device 5C is an FP that connects to the work route of the first logical path between the first relay device 5A. The MEP1 arranged at the FP111 monitors the OAM signal of the work route of the first logical path. The FP112 of the third relay device 5C is an FP that connects to the protection route of the first logical path between the fourth relay device 5D. The MEP2 arranged at the FP112 monitors the OAM signal of the protection route of the first logical path. DropFP1 of the third relay device 5C is an FP connected to the LAG of the second communication device 4B in the second MC-LAG section 2B. The virtual LAG of the third relay device 5C is an FP connected to the IPL of the fourth communication device 4D in the second MC-LAG section 2B.

[0052] The FP table 22 of the third relay device 5C stores, for example, “111” of FP111 and “112” of FP112 as the FPs used by the first logical path. st Tag ID is CVID “1”, VLAN 1 for FP111 and FP112 st The VID “11” is stored as the Tag ID. Furthermore, the FP table 22 stores the VLAN 2 nd Store CVID “1” as the Tag ID.

[0053] The MEP table 23 stores "1" for MEP1 as the MEP-ID, "111" for FP111 as the interface, and "1" for the opposite MEP1 as the peer MEP-ID. The MEP table 23 stores "2" for MEP2 as the MEP-ID, "112" for FP112 as the interface, and "2" for the opposite MEP2 as the peer MEP-ID.

[0054] FIG. 11 is an explanatory diagram showing an example of a provisioning model and a configuration table 15A of the fourth relay device 5D. For convenience of explanation, only the information of the FP related to the first logical path will be explained, and the explanation of the information of the FP related to the second logical path will be omitted. The fourth relay device 5D has an FP111, an FP112, a DropFP1, a virtual LAG, and an OAM filter. The fourth relay device 5D has a protection path of the first logical path in the linear protection section 3. The FP111 of the fourth relay device 5D is an FP that connects to the protection path of the first logical path between the fourth relay device 5D and the second relay device 5B. The FP112 of the fourth relay device 5D is an FP through which an OAM signal of the protection path of the first logical path between the fourth relay device 5D and the third relay device 5C flows. The DropFP1 of the fourth relay device 5D is an FP that connects to the LAG of the second communication device 4B in the second MC-LAG section 2B. The virtual LAG of the fourth relay device 5D is an IPL that connects to the third relay device 5C in the second MC-LAG section 2B. The OAM filter is a filter that transmits an OAM signal flowing from FP111 through the protection route of the first logical path and transfers it to FP112, and terminates the main signal flowing through the protection route of the first logical path at the termination point P12.

[0055] The FP table 22 of the fourth relay device 5D stores, for example, “111” of FP111 and “112” of FP112 as the FPs used by the first logical path. st Tag ID is CVID “1”, VLAN 1 for FP111 and FP112 stThe VID “11” is stored as the Tag ID. Furthermore, the FP table 22 stores the VLAN 2 nd Store CVID “1” as the Tag ID.

[0056] Next, the operation of the communication system 1 of this embodiment will be described. Fig. 12 is an explanatory diagram showing an example of the communication system 1 in the initial state. In the first MC-LAG section 2A of the communication system 1 in the initial state, the link between the first communication device 4A and the first relay device 5A is set to ACT, and the link between the first communication device 4A and the second relay device 5B is set to STBY. In the second MC-LAG section 2B of the communication system 1 in the initial state, the link between the second communication device 4B and the third relay device 5C is set to ACT, and the link between the second communication device 4B and the fourth relay device 5D is set to STBY.

[0057] In the linear protection section 3 of the communication system 1 in the initial state, the first starting point P1 of the first logical path is set to the first relay device 5A, and the second starting point P2 of the second logical path is set to the second relay device 5B. The first relay device 5A establishes a connection with the first communication device 4A in the first MC-LAG section 2A as the first starting point P1, and is capable of establishing a connection with the first communication device 4A in the first MC-LAG section 2A as the second starting point P2. Furthermore, in the linear protection section 3, the end point P11 of the Work route of the first logical path with respect to the first starting point P1 of the first logical path is set to the third relay device 5C. The third relay device 5C establishes a connection of the Work route of the linear protection method with the end point P11 of the first logical path with respect to the first starting point P1. Furthermore, in the linear protection section 3, it is assumed that the termination point P12 of the protection route of the first logical path with respect to the first starting point P1 of the first logical path is set to the fourth relay device 5D. The fourth relay device 5D establishes a connection of the protection route of the linear protection method as the termination point P12 of the first logical path with respect to the first starting point P1.

[0058] Furthermore, in the linear protection section 3, it is assumed that the end point P21 of the Work route of the second logical path with respect to the second starting point P2 of the second logical path is set to the third relay device 5C. The third relay device 5C establishes a connection of the Work route of the linear protection method with the end point P21 of the second logical path with respect to the second starting point P2. Furthermore, in the linear protection section 3, it is assumed that the end point P22 of the Protection route of the second logical path with respect to the second starting point P2 of the second logical path is set to the fourth relay device 5D. Furthermore, the fourth relay device 5D establishes a connection of the Protection route of the linear protection method with the end point P22 of the second logical path with respect to the second starting point P2.

[0059] The first communication device 4A is connected to the second communication device 4B via the third relay device 5C using the Work route of the first logical path from the first relay device 5A to the third relay device 5C.

[0060] FIG. 13 is an explanatory diagram showing an example of the communication system 1 when a failure occurs in the third relay device 5C. It is assumed that a failure occurs in the third relay device 5C from the initial state. When the third relay device 5C detects a failure in itself, it shuts down. The MEP1 and MEP2 of the first relay device 5A detect failures in both the work route and the protection route of the first logical path in the linear protection section 3 by the interruption of the OAM signal in response to the shutdown of the third relay device 5C. Furthermore, the MEP4 of the second relay device 5B also detects a failure in the work route of the second logical path in the linear protection section 3 by the interruption of the OAM signal in response to the shutdown of the third relay device 5C. Furthermore, the MEP4 of the fourth relay device 5D also detects a failure in the work route of the second logical path in the linear protection section 3 by the interruption of the OAM signal in response to the shutdown of the third relay device 5C.

[0061] Furthermore, the second relay device 5B detects a LAG failure due to disconnection of LACP (Link Aggregation Control Protocol) between the second relay device 5B and the third relay device 5C in the second MC-LAG section 2B in response to the shutdown of the third relay device 5C. Furthermore, the fourth relay device 5D also detects an IPL failure due to disconnection of the IPL between the second relay device 5B and the third relay device 5C in the second MC-LAG section 2B in response to the shutdown of the third relay device 5C.

[0062] 14 is an explanatory diagram showing an example of the communication system 1 when a default route is set. When the first relay device 5A detects failures in both the Work route and the Protection route of the first logical path in the linear protection section 3 by MEP1 and MEP2, the first relay device 5A autonomously switches the Work route of the first logical path to a default route. The default route is a route from the first starting point P1 of the first logical path of the first relay device 5A to the second relay device 5B to the ending point P21 of the first logical path of the fourth relay device 5D.

[0063] When the second relay device 5B detects a failure of the work route of the second logical path due to the interruption of the OAM signal in the linear protection section 3 by the MEP4, it connects to the termination point P21 of the first logical path of the fourth relay device 5D using the work route of the first logical path as a default route. Furthermore, when the fourth relay device 5D detects a failure of the work route of the second logical path due to the interruption of the OAM signal in the linear protection section 3 by the MEP4, it switches the work route of the first logical path to the default route, connects to the second relay device 5B, and sets it to the termination point P21 of the work route of the first logical path. As a result, in the linear protection section 3, the first logical path is switched to the default route from the first starting point P1 of the first relay device 5A to the second relay device 5B to the termination point P21 of the fourth relay device 5D. Then, the main signal of the first logical path travels from the first starting point P1 through the second repeater 5B and terminates at the termination point P21 of the fourth repeater 5D. Note that in the linear protection section 3, although the main signal is terminated at the termination point P21 of the fourth repeater 5D, the OAM signal is not terminated but is transparently forwarded to the MEP2 in the third repeater 5C. As a result, the MEP2 of the first repeater 5A and the MEP2 of the third repeater can monitor the route status of the default route with the OAM signal even after switching to the default route.

[0064] When the fourth relay device 5D detects a disconnection of the IPL with the third relay device 5C in the second MC-LAG section 2B, it autonomously switches the link with the second communication device 4B in the second MC-LAG section 2B from STBY to ACT. Furthermore, the second communication device 4B autonomously switches the link with the third relay device 5C from ACT to STBY and the link with the fourth relay device 5D from STBY to ACT in response to the shutdown of the third relay device 5C in the second MC-LAG section 2B. Note that the second communication device 4B autonomously switches the links within, for example, one second after the detection of the failure.

[0065] As a result, when the first relay device 5A detects failures of both systems caused by MEP1 and MEP2, it autonomously switches the Work route of the first logical path to a default route in the linear protection section 3, thereby enabling communication to be restored via the route from the first relay device 5A to the second relay device 5B to the fourth relay device 5D to the second communication device 4B. In the communication system 1, even if ACT / STBY switching occurs in the second MC-LAG section 2B, the termination point of the linear protection section 3 is not changed. Then, when the fourth relay device 5D detects a break in the IPL with the third relay device 5C, it autonomously switches the link with the second communication device 4B in the second MC-LAG section 2B from STBY to ACT. That is, when the first relay device 5A detects both system failures caused by MEP1 and MEP2, it switches to the default route, and furthermore, the fourth relay device 5D forcibly switches the link with the second communication device 4B in the second MC-LAG section 2B to ACT. As a result, since communication is established through the route of the first communication device 4A → the first relay device 5A → the second relay device 5B → the fourth relay device 5D → the second communication device 4B, it is possible to suppress return communication between the third relay device 5C and the fourth relay device 5D. Therefore, it is possible to suppress a decrease in communication efficiency. Also, in the communication system 1, the first MC-LAG section 2A, the second MC-LAG section 2B, and the linear protection section 3 are autonomously switched.

[0066] Next, an operation when the failure of the third relay device 5C is recovered from the state of the communication system 1 shown in FIG. 14 will be described. FIG. 15 is an explanatory diagram showing an example of the communication system 1 when the failure of the third relay device 5C is recovered. When the third relay device 5C recovers from the failure, the shutdown is released. The MEP1 of the first relay device 5A detects the failure recovery of the third relay device 5C in response to the OAM signal. The MEP4 of the second relay device 5B also detects the failure recovery of the third relay device 5C in response to the OAM signal. Furthermore, the MEP4 of the fourth relay device 5D also detects the failure recovery of the third relay device 5C in response to the OAM signal.

[0067] Fig. 16A is an explanatory diagram showing an example of the communication system 1 when the third relay device 5C recovers from a failure. In Fig. 16A, the first relay device 5A starts a timer when it detects recovery from failures on both the Work path and the Protection path of the first logical path in response to the release of the shutdown of the third relay device 5C. Furthermore, the second relay device 5B and the fourth relay device 5D also detect recovery from failure of the third relay device 5C in response to the OAM signal. The second relay device 5B and the fourth relay device 5D also start a timer when it detects recovery from failure of the third relay device 5C.

[0068] Fig. 16B is an explanatory diagram showing an example of the communication system 1 when the Work route is switched back when the third relay device 5C recovers from a failure. In Fig. 16B, when the first relay device 5A in the linear protection section 3 detects that a timer has expired, it switches back from the default route of the first logical path to the Work route. Furthermore, when the second relay device 5B in the linear protection section 3 detects that a timer has expired, it also switches back from the Protection route of the second logical path to the Work route. There is no link switching operation in the second MC-LAG section 2B.

[0069] As a result, the first communication device 4A uses the Work route of the switchback of the first logical path from the first starting point P1 of the first relay device 5A to the third relay device 5C, and transmits the main signal to the second communication device 4B via the route from the third relay device 5C to the fourth relay device 5D.

[0070] The first relay device 5A of the first embodiment establishes a connection with the first communication device 4A as the first starting point P1 of the first logical path of the linear protection method. The third relay device 5C establishes a connection of the first logical path in the first route of the linear protection method as the end point P11 of the first logical path for the first starting point P1, and executes communication with the second communication device 4B. The fourth relay device 5D establishes a connection of the first logical path in the second route of the linear protection method as the end point P12 of the first logical path for the first starting point P1, and executes communication with the second communication device 4B. Since there are two end points for the first starting point P1 of the first logical path, even if a failure occurs on the route of one end point, it is possible to terminate the main signal by using the other end point and suppress return communication between the third relay device 5C and the fourth relay device 5D. As a result, it is possible to improve communication efficiency and communication reliability.

[0071] In the linear protection section 3, when the third relay device 5C is abnormal, the first logical path connection is established in the default route from the first starting point P1 to the second end point P12 in the fourth relay device 5D via the second relay device 5B. Then, the connection between the third relay device 5C and the second communication device 4B, which is activated in the second MC-LAG method, is deactivated (STBY). Furthermore, the connection between the fourth relay device 5D and the second communication device 4B is activated (ACT) to execute communication with the second communication device 4B. That is, when the first relay device 5A detects, for example, a double-system failure of the first logical path, it sets the default route and forcibly switches the link between the fourth relay device 5D and the second communication device 4B to ACT. As a result, the communication reliability is ensured by using the default route, and the communication efficiency is improved by suppressing the return communication between the third relay device 5C and the fourth relay device 5D.

[0072] The termination point P12 in the fourth relay device 5D terminates the main signal of the first logical path received from the first starting point P1 in the first relay device 5A via the default route. As a result, since there are two termination points for the first starting point P1 of the first logical path, even if a failure occurs on the route of one of the termination points, the main signal can be terminated by using the other termination point, and return communication between the third relay device 5C and the fourth relay device 5D can be suppressed. As a result, communication efficiency and communication reliability can be improved.

[0073] Furthermore, the termination point P12 transfers the OAM signal of the first logical path received from the first starting point P1 via the default route to the third relay device 5C. As a result, the MEP2 of the first relay device 5A and the MEP2 of the third relay device 5C can monitor the route status on the default route even if the main signal is terminated at the fourth relay device 5D.

[0074] When the first relay device 5A detects a double-sided failure of the first logical path, it sets a default route of the first logical path. Furthermore, when the fourth relay device 5D detects an IPL failure between the fourth relay device 5D and the third relay device 5C of the second MC-LAG system, it sets the connection between the fourth relay device 5D and the second communication device 4B to ACT. As a result, the communication reliability is ensured by using the default route, and the communication efficiency is improved by suppressing return communication between the third relay device 5C and the fourth relay device 5D.

[0075] The second relay device 5B establishes a connection with the first communication device 4A as the second starting point P2 of the second logical path of the linear protection method. The third relay device 5C establishes a connection of the second logical path in the third route of the linear protection method as the end point P21 of the second logical path for the second starting point P2, and executes communication with the second communication device 4B. The fourth relay device 5D establishes a connection of the second logical path in the fourth route of the linear protection method as the end point P22 of the second logical path for the second starting point P2, and executes communication with the second communication device 4B. As a result, since there are two end points for the second starting point P2 of the second logical path, even if a failure occurs on the route of one end point, it is possible to terminate the main signal by using the other end point and suppress return communication between the third relay device 5C and the fourth relay device 5D. As a result, it is possible to improve communication efficiency and communication reliability.

[0076] In the linear protection section 3, when the fourth relay device 5D is abnormal, the second logical path from the second starting point P2 is established in the default route to the first end point P21 in the third relay device 5C via the first relay device 5A. Then, the connection between the fourth relay device 5D and the second communication device 4B, which is activated in the second MC-LAG method, is deactivated (STBY). Furthermore, the connection between the third relay device 5C and the second communication device 4B is activated (ACT) to execute communication with the second communication device 4B. That is, when the second relay device 5B detects, for example, a double-system failure of the second logical path, it sets the default route and forcibly switches the link between the third relay device 5C and the second communication device 4B to ACT. As a result, the communication reliability is ensured by using the default route, and the communication efficiency is improved by suppressing the return communication between the third relay device 5C and the fourth relay device 5D.

[0077] The termination point P21 in the third relay device 5C terminates the main signal of the second logical path received from the second starting point P2 in the second relay device 5B via the default route. As a result, since there are two termination points for the second starting point P2 of the second logical path, even if a failure occurs on the route of one of the termination points, the main signal can be terminated by using the other termination point, and return communication between the third relay device 5C and the fourth relay device 5D can be suppressed. As a result, communication efficiency and communication reliability can be improved.

[0078] Furthermore, the termination point P21 transfers the OAM signal of the second logical path received from the second starting point P2 via the default route to the fourth relay device 5D. As a result, the MEP4 of the second relay device 5B and the MEP4 of the fourth relay device 5D can monitor the route status on the default route even if the main signal is terminated at the third relay device 5C.

[0079] When the second relay device 5B detects a double-sided failure of the second logical path, it sets a default route of the second logical path. Furthermore, when the third relay device 5C detects an IPL failure between the second relay device 5C and the fourth relay device 5D of the second MC-LAG system, it sets the connection with the second communication device 4B to ACT. As a result, the communication reliability is ensured by using the default route, and the communication efficiency is improved by suppressing return communication between the third relay device 5C and the fourth relay device 5D.

[0080] For ease of explanation, a communication system 1 in which a main signal flows from a first communication device 4A to a second communication device 4B has been described as an example, but the present invention is also applicable to a communication system in which a main signal flows from a second communication device 4B to a first communication device 4A.

[0081] In addition, the linear protection section 3 has been described using G.8031, but it may be G.8131, and can be changed as appropriate. In G.8131, the VLAN 1 st Tag ID and VLAN 2 nd Label 1, which shows the ID of the label instead of Tag ID st ID and Label 2 ndID shall be used.

[0082] In the above description, the route from the first relay device 5A to the third relay device 5C of the first logical path is set as the Work route, and the route from the first relay device 5A to the fourth relay device 5D via the second relay device 5B is set as the Protection route. However, the Work route and the Protection route of the first logical path may be set inversely, and can be changed as appropriate. The same applies to the second logical path. In the communication system 1 of the first embodiment, the MC-LAG section is described as having an ACT / STBY configuration, but since the ACT / ACT configuration can also be applied, an embodiment of the ACT / ACT configuration will be described below as a second embodiment. EXAMPLES

[0083] Fig. 17A is an explanatory diagram showing an example of a communication system 1 (MC-LAG ACT / ACT) of a second embodiment, and Fig. 17B is an explanatory diagram showing an example of a provisioning model of the communication system 1. Note that the same components as those in the communication system 1 of the first embodiment are given the same reference numerals, and descriptions of the overlapping components and operations are omitted. The communication system 1 shown in Fig. 17A has a configuration in which a first MC-LAG section 2A of an ACT / ACT configuration, a second MC-LAG section 2B of an ACT / ACT configuration, and a linear protection section 3 are arranged between a first communication device 4A and a second communication device 4B.

[0084] In the first MC-LAG section 2A, for example, the link between the first communication device 4A and the first relay device 5A is set to ACT, and the link between the first communication device 4A and the second relay device 5B is set to ACT. ACT is a state in which the link (connection) between the devices is activated. The link switching time in the first MC-LAG section 2A is, for example, within one second. Furthermore, in the second MC-LAG section 2B, for example, the link between the second communication device 4B and the third relay device 5C is set to ACT, and the link between the second communication device 4B and the fourth relay device 5D is set to ACT. The link switching time in the second MC-LAG section 2B is, for example, within one second.

[0085] The first relay device 5A of the second embodiment establishes a connection with the first communication device 4A as the first starting point P1 of the first logical path of the linear protection method. The third relay device 5C establishes a connection of the first logical path in the first route of the linear protection method as the end point P11 of the first logical path with respect to the first starting point P1, and executes communication with the second communication device 4B. The fourth relay device 5D establishes a connection of the first logical path in the second route of the linear protection method as the end point P12 of the first logical path with respect to the first starting point P1, and executes communication with the second communication device 4B. Since there are two end points with respect to the first starting point P1 of the first logical path, even if a failure occurs on the route of one end point, it is possible to terminate the main signal by using the other end point and suppress return communication between the third relay device 5C and the fourth relay device 5D. As a result, even if the first MC-LAG section 2A and the second MC-LAG section 2B have an ACT / ACT configuration, it is possible to improve communication efficiency and communication reliability.

[0086] In the linear protection section 3, when the third relay device 5C is abnormal, the first logical path is established in a default route from the first starting point P1 to the second ending point P12 in the fourth relay device 5D via the second relay device 5B. For example, when the first relay device 5A detects a failure on both sides of the first logical path, it sets the default route. As a result, even if the first MC-LAG section 2A and the second MC-LAG section 2B are in an ACT / ACT configuration, the communication reliability is ensured by using the default route, and the communication efficiency is improved by suppressing return communication between the third relay device 5C and the fourth relay device 5D.

[0087] The termination point P12 in the fourth relay device 5D terminates the main signal of the first logical path received from the first starting point P1 in the first relay device 5A via the default route. As a result, since there are two termination points for the first starting point P1 of the first logical path, even if a failure occurs on the route of one of the termination points, the main signal can be terminated by using the other termination point, and return communication between the third relay device 5C and the fourth relay device 5D can be suppressed. As a result, even if the first MC-LAG section 2A and the second MC-LAG section 2B are in an ACT / ACT configuration, communication efficiency and communication reliability can be improved.

[0088] Furthermore, the termination point P12 transfers the OAM signal of the first logical path received from the first initiation point P1 via the default route to the third relay device 5C. As a result, even if the first MC-LAG section 2A and the second MC-LAG section 2B are in an ACT / ACT configuration, the MEP2 of the first relay device 5A and the MEP2 of the third relay device 5C can monitor the route status on the default route even if the main signal is terminated at the fourth relay device 5D.

[0089] When the first relay device 5A detects a double-system failure of the first logical path, it sets a default route of the first logical path. Furthermore, when the fourth relay device 5D detects an IPL failure between the fourth relay device 5D and the third relay device 5C of the second MC-LAG system, it sets the connection between the fourth relay device 5D and the second communication device 4B to ACT. As a result, even if the first MC-LAG section 2A and the second MC-LAG section 2B are in an ACT / ACT configuration, communication reliability is ensured by using the default route, and return communication between the third relay device 5C and the fourth relay device 5D is suppressed, thereby improving communication efficiency.

[0090] The second relay device 5B establishes a connection with the first communication device 4A as the second starting point P2 of the second logical path of the linear protection method. The third relay device 5C establishes a connection of the second logical path in the third route of the linear protection method as the end point P21 of the second logical path to the second starting point P2, and executes communication with the second communication device 4B. The fourth relay device 5D establishes a connection of the second logical path in the fourth route of the linear protection method as the end point P22 of the second logical path to the second starting point P2, and executes communication with the second communication device 4B. As a result, since there are two end points for the second starting point P2 of the second logical path, even if a failure occurs on the route of one end point, it is possible to terminate the main signal by using the other end point and suppress return communication between the third relay device 5C and the fourth relay device 5D. As a result, even if the first MC-LAG section 2A and the second MC-LAG section 2B have an ACT / ACT configuration, it is possible to improve communication efficiency and communication reliability.

[0091] In the linear protection section 3, when the fourth relay device 5D is abnormal, the second logical path from the second starting point P2 is established on a default route that leads to the first ending point P21 in the third relay device 5C via the first relay device 5A. For example, when the second relay device 5B detects a failure on both sides of the second logical path, it is set to the default route. As a result, even if the first MC-LAG section 2A and the second MC-LAG section 2B are in an ACT / ACT configuration, the communication reliability is ensured by using the default route, and the communication efficiency is improved by suppressing return communication between the third relay device 5C and the fourth relay device 5D.

[0092] The termination point P21 in the third relay device 5C terminates the main signal of the second logical path received from the second starting point P2 in the second relay device 5B via the default route. As a result, since there are two termination points for the second starting point P2 of the second logical path, even if a failure occurs on the route of one of the termination points, the main signal can be terminated by using the other termination point, and return communication between the third relay device 5C and the fourth relay device 5D can be suppressed. As a result, even if the first MC-LAG section 2A and the second MC-LAG section 2B are in an ACT / ACT configuration, communication efficiency and communication reliability can be improved.

[0093] Furthermore, the termination point P21 transfers the OAM signal of the second logical path received from the second starting point P2 via the default route to the fourth relay device 5D. As a result, the MEP4 of the second relay device 5B and the MEP4 of the fourth relay device 5D can monitor the route state on the default route even if the first MC-LAG section 2A and the second MC-LAG section 2B are in the ACT / ACT configuration and even if the main signal is terminated at the third relay device 5C.

[0094] When the second relay device 5B detects a double-sided failure of the second logical path, it sets a default route of the second logical path. Furthermore, when the third relay device 5C detects an IPL failure between the second relay device 5C and the fourth relay device 5D of the second MC-LAG system, it sets the connection between the second relay device 5C and the second communication device 4B to ACT. As a result, even if the first MC-LAG section 2A and the second MC-LAG section 2B are in an ACT / ACT configuration, communication reliability is ensured by using the default route, and return communication between the third relay device 5C and the fourth relay device 5D is suppressed, thereby improving communication efficiency.

[0095] Furthermore, each component of each unit shown in the figure does not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each unit is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0096] Furthermore, the linear protection section 3, the first MC-LAG section 2A, and the second MC-LAG section 2B are not subject to geographical restrictions, and the distances therebetween may be short or long.

[0097] Furthermore, the various processing functions performed by each device may be executed in whole or in part on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit) or an MCU (Micro Controller Unit)). It goes without saying that the various processing functions may be executed in whole or in part on a program analyzed and executed by a CPU (or a microcomputer such as an MPU or an MCU), or on hardware using wired logic. [Explanation of symbols]

[0098] 1. Communication Systems 2A First MC-LAG Section 2B Second MC-LAG section 3 Linear protection section 4A First communication device 4B Second communication device 5A First relay device 5B Second relay device 5C Third relay device 5D 4th relay device P1 First starting point P2 Second starting point P11, P12, P21, P22 Termination point

Claims

1. A communication system including a first relay device and a second relay device connected to a first communication device by a first MC-LAG (Multi-Chassis Link Aggregation) method, and a third relay device and a fourth relay device connected to the second communication device by a second MC-LAG method, and connecting the first relay device and the third relay device, the first relay device and the second relay device, the second relay device and the fourth relay device, and the third relay device and the fourth relay device by a linear protection method, The first relay device is The first communication device is set as a starting point of a logical path of the linear protection method, and a connection is established with the first communication device; The third relay device is a first communication device that is set as a first termination point of the logical path with respect to the starting termination point, establishes a connection of the logical path in a first route of the linear protection method, and executes communication with the second communication device; The fourth relay device is A communication system characterized in that the logical path is set as a second termination point for the logical path with respect to the starting point, the logical path is connected in a second route of the linear protection method, and communication is performed with the second communication device.

2. The communication system includes: establishing a connection of the logical path on the first route when the third relay device is normal; The communication system according to claim 1, characterized in that, when the third relay device is abnormal, a connection of the logical path on the second route from the starting point to the second termination point in the fourth relay device via the second relay device is established, the connection between the third relay device and the second communication device that is activated in the second MC-LAG method is deactivated, and the connection between the fourth relay device and the second communication device is activated, thereby performing communication with the second communication device.

3. The fourth relay device is The communication system according to claim 2, characterized in that, when a failure is detected between the second communication device and the third relay device of the second MC-LAG method, a connection between the second communication device and the third relay device is activated.

4. The fourth relay device is A communication system as described in claim 2 or 3, characterized in that a connection of the logical path on the second route is established, main signal communication is performed with the second communication device, and maintenance signal communication is performed with the third relay device.

5. The second relay device is a second communication device that is set as another starting point of the logical path of the linear protection method and establishes a connection with the first communication device; The third relay device is a third end point of the logical path for the other start point is set, a connection of the logical path in a third route of the linear protection method is established, and communication with the second communication device is performed; The fourth relay device is The communication system according to claim 1, characterized in that the communication system is set as a fourth termination point of the logical path with respect to the other starting point, establishes a connection of the logical path in a fourth route of the linear protection method, and performs communication with the second communication device.

6. The communication system includes: establishing a connection of the logical path on the fourth route when the fourth relay device is normal; The communication system according to claim 5, characterized in that, when the fourth relay device is abnormal, a connection of the logical path on the third route from the other starting point to the third termination point in the third relay device via the first relay device is established, the connection between the fourth relay device and the second communication device that is activated in the second MC-LAG method is deactivated, and the connection between the third relay device and the second communication device is activated, thereby performing communication with the second communication device.

7. The third relay device is The communication system according to claim 6, characterized in that, when a failure is detected between the fourth relay device of the second MC-LAG method, a connection between the second communication device is activated.

8. A relay device that is connected to a first communication device together with a paired relay device in a first MC-LAG (Multi-Chassis Link Aggregation) manner, and that is connected to a second communication device in a second MC-LAG manner, and that is connected to one of the opposing relay devices and to the other of the opposing relay devices in a linear protection manner, The first communication device is set as a starting point of a logical path of the linear protection method, and a connection is established with the first communication device; a first relay device that is set as a first termination point of the logical path with respect to the starting point and that establishes a connection of the logical path in a first route of the linear protection method, and executes communication with the second communication device via the first relay device; A relay device that is set as a second termination point of the logical path for the starting point, connects to the other relay device that establishes a connection of the logical path in the second route of the linear protection method, and performs communication with the second communication device via the other relay device.

9. A communication method for a communication system having a first relay device and a second relay device connected to a first communication device by a first MC-LAG (Multi-Chassis Link Aggregation) method, and a third relay device and a fourth relay device connected to the second communication device by a second MC-LAG method, the system connecting the first relay device and the third relay device, the first relay device and the second relay device, the second relay device and the fourth relay device, and the third relay device and the fourth relay device by a linear protection method, The first relay device, The first communication device is set as a starting point of a logical path of the linear protection method, and a connection is established with the first communication device; The third relay device, a first communication device that is set as a first termination point of the logical path with respect to the starting termination point, establishes a connection of the logical path in a first route of the linear protection method, and executes communication with the second communication device; The fourth relay device, A second communication device is set as a second end point of the logical path with respect to the starting end point, and establishes a connection of the logical path in a second route of the linear protection method, and executes communication with the second communication device. A communication method comprising: executing a process.

10. The communication system includes: establishing a connection of the logical path on the first route when the third relay device is normal; The communication method according to claim 9, characterized in that, when the third relay device is abnormal, a connection of the logical path on the second route from the starting point to the second termination point in the fourth relay device via the second relay device is established, the connection between the third relay device and the second communication device that is activated in the second MC-LAG method is deactivated, and the connection between the fourth relay device and the second communication device is activated, thereby performing communication with the second communication device.

11. The fourth relay device is The communication method according to claim 10, characterized in that, when a failure is detected between the third relay device of the second MC-LAG method, a connection between the second communication device and the third relay device is activated.

12. The fourth relay device is The communication method according to claim 10 or 11, characterized in that a connection of the logical path in the second route is established, and communication of a main signal with the second communication device is performed, while communication of a maintenance signal with the third relay device is performed.

13. The second relay device is a second communication device that is set as another starting point of the logical path of the linear protection method and establishes a connection with the first communication device; The third relay device is a third end point of the logical path for the other start point is set, a connection of the logical path in a third route of the linear protection method is established, and communication with the second communication device is performed; The fourth relay device is The communication method according to claim 9, characterized in that the second communication device is set as a fourth termination point of the logical path relative to the other starting point, a connection of the logical path in a fourth route of the linear protection method is established, and communication with the second communication device is performed.

14. The communication system includes: establishing a connection of the logical path on the fourth route when the fourth relay device is normal; The communication method according to claim 13, characterized in that, when the fourth relay device is abnormal, a connection of the logical path on the third route from the other starting point to the third termination point in the third relay device via the first relay device is established, the connection between the fourth relay device and the second communication device that is activated in the second MC-LAG method is deactivated, and the connection between the third relay device and the second communication device is activated, thereby performing communication with the second communication device.

15. The third relay device is The communication method according to claim 12, characterized in that, when a failure is detected between the fourth relay device of the second MC-LAG method, a connection between the second communication device and the fourth relay device is activated.

Images