COMMUNICATION SYSTEM, COMMUNICATION DEVICE, AND COMMUNICATION CONTROL METHOD

Abstract

To provide a communication system, a communication device, and a communication control method, for eliminating learning of a client MAC address and enabling frame transfer between nodes constituting a ring network without depending on a specific technique.SOLUTION: A communication system 100 comprises a plurality of communication devices that constitute a ring network and construct one-to-one connection topology with a counter device. A closed link is set in the ring network. Each of the plurality of communication devices monitors conduction of the ring network to learn a MAC (Media Access Control) address of the counter device on the ring network, stores a table in which the learned MAC address is associated with a ring port, and transfers a frame on the ring network on the basis of the table.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] There is known a ring network formed by connecting a plurality of nodes in a ring shape. For example, ITU-T (International Telecommunication Union Telecommunication Standardization Sector) G.8032 (Non-Patent Document 1) specifies Ethernet (registered trademark) Ring Protection (ERP).

[0003] In ITU-T G.8032 ERP, in a ring network using Ethernet (registered trademark), a blocked link (Ring Protection Link) is set to prevent the occurrence of a route loop. Continuity is monitored between the nodes constituting the ring, and if a fault is detected during the continuity monitoring, the link is unblocked and the MAC address learning table (also called FDB: Filtering Data Base) that records the MAC (Media Access Control) addresses learned in each node is flushed. Next, each node relearns the MAC address by flooding packets, and updates the FDB with the learned MAC address. By relearning the MAC address when a link fault occurs, the frame forwarding route can be switched. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] ITU-T G.8032 / Y.1344(03 / 2020) "Ethernet ring protection switching", [online], [Retrieved December 10, 2020], Internet<URL:https: / / www.itu.int / rec / dologin_pub.asp?lang=e&id=T-REC-G.8032-202003-I!!PDF-E&type=items> Summary of the Invention [Problem to be solved by the invention]

[0005] For example, there are networks such as metro networks and backbone networks through which data from many users (clients) passes. If each node in such a network were to learn the MAC addresses of the clients it accommodates, a huge FDB would be required.

[0006] One method that can solve such problems is PBB (Provider Backbone Bridge) defined in IEEE (Institute of Electrical and Electronics Engineers) 802.1ah (IEEE is a registered trademark). In IEEE 802.1ah PBB, data from each client is encapsulated according to a method known as MAC-in-MAC. In the MAC-in-MAC method, each node hides the client's MAC address and learns only the MAC addresses of the nodes that make up the metro network or backbone network. This makes it possible to significantly reduce the number of MAC addresses that need to be learned within each node.

[0007] When a frame is sent from a PBB edge node to a backbone network, the output port of the edge node is determined using the destination address (B-MAC DA) in the PBB header. In a normal bridge, the output destination of a frame is determined by searching the FDB using the B-MAC DA as a key. However, some switches that support the PBB function, when operating as a PBB edge node, do not search the FDB in the process of determining the output port after encapsulation, but instead determine the output destination by referring to a table independent of the FDB. In the case of devices with this type of function, the output port cannot be automatically determined by simply executing the process at the time of a link failure specified in ITU-T G.8032.

[0008] Meanwhile, methods have also been proposed for determining the output destination of a frame without relying on MAC address learning at layer 2. For example, RFC (Request For Comments) 7623 and RFC 6329 propose a method for determining the output destination without relying on MAC address learning at layer 2 by extending routing protocols such as BGP (Border Gateway Protocol) or IS-IS (Intermediate System to Intermediate System) to transmit B-MAC and I-SID information on the control plane. However, there is a problem in that the nodes that make up the ring must support BGP / IS-IS, which increases the requirements placed on the nodes.

[0009] An object of the present disclosure is to provide a communication system, a communication device, and a communication control method that enable the transfer of frames between nodes that form a ring network without the need to learn client MAC addresses and without relying on a specific method. [Means for solving the problem]

[0010] The communication system of the present disclosure includes a plurality of communication devices that configure a ring network and establish a one-to-one connection topology with a counterpart device. A blocked link is set in the ring network. Each of the plurality of communication devices monitors the continuity of the ring network, learns the MAC (Media Access Control) addresses of the counterpart devices on the ring network, stores a table that associates the learned MAC addresses with ring ports, and transfers frames on the ring network based on the table.

[0011] The communication device disclosed herein is a communication device that is provided on a ring network and establishes a one-to-one connection topology with a counterpart device on the ring network, and includes a monitoring unit that monitors continuity with the counterpart device, a MAC address learning unit that learns the MAC (Media Access Control) address of the counterpart device based on the results of the continuity monitoring and stores a table that associates the learned MAC address with a ring port, a service path setting unit that sets a service path, which is a logical path connecting the communication device and the counterpart device, and a service path forwarding unit that forwards frames according to the service path set by the service path setting unit.

[0012] The communication control method disclosed herein is a communication control method in a ring network composed of a plurality of communication devices that establish a one-to-one connection topology with a counterpart device and in which a blocked link is set, and includes the steps of causing each of the plurality of communication devices to learn the MAC (Media Access Control) address of the counterpart device through monitoring continuity of the ring network, causing each of the plurality of communication devices to update a table that associates MAC addresses with ring ports with the learned MAC address, and forwarding frames on the ring network based on the table.

[0013] The communication control method disclosed herein is a communication control method by a communication device that is provided on a ring network and establishes a one-to-one connection topology with a counterpart device on the ring network, and includes the steps of monitoring continuity with the counterpart device, learning the MAC (Media Access Control) address of the counterpart device based on the results of the continuity monitoring, updating a table associating MAC addresses with ring ports of the communication device with the learned MAC address, setting a service path, which is a logical path connecting the communication device and the counterpart device, and forwarding frames according to the set service path. Effect of the Invention

[0014] According to the present disclosure, it is possible to transfer frames between nodes that form a ring network without the need to learn client MAC addresses and without relying on a specific method. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating a configuration example of a communication system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a block diagram illustrating a configuration of a communication device according to an embodiment of the present disclosure. [Diagram 3] FIG. 3 is a diagram for explaining the addition and deletion of a VLAN tag in the transfer of a data frame according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a flowchart illustrating a normal operation of the communication system according to the embodiment of the present disclosure. [Diagram 5] FIG. 5 is a flowchart for explaining the operation of a node when the ring configuration is changed. [Figure 6] FIG. 6 is a diagram illustrating an example of a redundant configuration of a communication system according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described.

[0017] (1) A communication system according to an embodiment of the present disclosure includes a plurality of communication devices that configure a ring network and establish a one-to-one connection topology with a corresponding device. A blocked link is set in the ring network. Each of the plurality of communication devices monitors continuity of the ring network, learns the MAC (Media Access Control) addresses of the corresponding devices on the ring network, stores a table that associates the learned MAC addresses with ring ports, and transfers frames on the ring network based on the table.

[0018] According to this configuration, each communication device stores a table that associates the learned MAC address of the opposing device with the ring port of the communication device. The forwarding destination of a frame is determined based on this table. Therefore, there is no need to learn the MAC addresses of clients accommodated in each communication device. Furthermore, since the output destination of a frame can be determined using the FDB, it becomes possible to forward frames without relying on a specific method (for example, determining the output destination of a frame using a table other than the FDB).

[0019] (2) In the communication system described in (1) above, when each of the multiple communication devices receives a frame to be forwarded to a corresponding device from a client port, it assigns a VLAN tag to the frame, the VLAN tag including a VLAN ID assigned for communication with the corresponding device.

[0020] According to this configuration, it is possible to transfer frames without being limited to a specific method. For example, the embodiment of the present disclosure is applicable to the PBB defined in IEEE802.1ah, but is not limited to being applied only to the PBB. However, according to the above configuration, it is possible to realize frame transfer more easily than encapsulation in IEEE802.1ah PBB.

[0021] (3) In the communication system described in (2) above, each of the multiple communication devices sets a UP MEP (Maintenance association End Point) on one of the client ports belonging to the VLAN ID to monitor the continuity of the ring network, and transmits and receives messages in accordance with Ethernet OAM (Operations, Administration, Maintenance).

[0022] According to this configuration, by using the UP MEP in each communication device, the CCM frame is forwarded via the switch function. Therefore, no matter which ring port of the communication device the opposite device is connected to, the MAC address can be learned. Therefore, in each communication device, the ring port to which the frame should be output can be determined.

[0023] (4) In a communication system described in any one of (1) to (3) above, if a fault in the ring network is detected during monitoring of the continuity of the ring network, the blocked link is opened and the multiple communication devices re-learn the MAC addresses to update the association between the MAC addresses and the ring ports in the table.

[0024] According to this configuration, if a fault occurs on the ring network, the ring port to output the frame can be re-determined by relearning the MAC address, so that the frame forwarding path can be switched when a fault occurs on the ring network.

[0025] (5) In a communication system according to any one of (1) to (4) above, at least one of the plurality of communication devices has a redundant configuration including an active system and a standby system, and when continuity of the ring network through the active system is not possible, forwards frames on the ring network based on a table of the standby system.

[0026] According to this configuration, since the communication device has a redundant function, when a failure occurs in the active system, the port for transferring frames can be switched to the standby system, and therefore, frame transfer can be continued.

[0027] (6) In a communication system according to any one of (1) to (5) above, the plurality of communication devices include at least one communication device corresponding to an aggregation node and at least one communication device corresponding to a client accommodating node, and the aggregation node and the client accommodating node form a service path, which is a logical route connecting the aggregation node and the client accommodating node.

[0028] According to the above, each of the aggregation node and the client accommodating node can transmit using the service path based only on the MAC address of the node facing the node itself. Therefore, since it is not necessary to learn the MAC address of the client, the size of the MAC address learning table can be suppressed.

[0029] (7) The communication system according to any one of (1) to (6) above includes at least one communication device corresponding to an aggregation node, and a plurality of communication devices each corresponding to a client accommodation node.

[0030] According to the above, a frame accommodated in each client accommodating node can be transferred without referring to the client MAC address in the frame.

[0031] (8) A communication device according to an embodiment of the present disclosure is provided on a ring network and establishes a one-to-one connection topology with a counterpart device on the ring network, and includes a monitoring unit that monitors continuity with the counterpart device, a MAC address learning unit that learns the MAC (Media Access Control) address of the counterpart device based on the results of the continuity monitoring and stores a table that associates the learned MAC address with a ring port, a service path setting unit that sets a service path, which is a logical path connecting the communication device and the counterpart device, and a service path forwarding unit that forwards frames in accordance with the service path set by the service path setting unit.

[0032] According to this configuration, the communication device learns the MAC address of the opposing device and associates the MAC address with the ring port of the communication device. This eliminates the need to learn client MAC addresses when two communication devices on a ring network build a one-to-one connection topology. Furthermore, the communication device sets a service path and transfers frames along that service path. This makes it possible to transfer frames between nodes building a ring network without relying on a specific method (for example, determining the output destination of a frame using a table other than the FDB).

[0033] (9) A communication control method according to an embodiment of the present disclosure is a communication control method in a ring network configured with a plurality of communication devices that establish a one-to-one connection topology with a counterpart device and in which a blocked link is set, the method comprising the steps of: causing each of the plurality of communication devices to learn a MAC (Media Access Control) address of the counterpart device through monitoring continuity of the ring network; causing each of the plurality of communication devices to update a table that associates MAC addresses with ring ports with the learned MAC address; and forwarding frames on the ring network based on the table.

[0034] According to this configuration, it is not necessary to learn client MAC addresses, and frames can be transferred between nodes that form a ring network without depending on a specific method.

[0035] (10) A communication control method according to an embodiment of the present disclosure is a communication control method by a communication device that is provided on a ring network and establishes a one-to-one connection topology with a counterpart device on the ring network, comprising the steps of: monitoring continuity with the counterpart device; learning a Media Access Control (MAC) address of the counterpart device based on a result of the continuity monitoring; updating a table associating MAC addresses with ring ports of the communication device with the learned MAC address; setting a service path, which is a logical path connecting the communication device and the counterpart device; and forwarding frames according to the set service path.

[0036] According to this configuration, it is not necessary to learn client MAC addresses, and frames can be transferred between nodes that form a ring network without depending on a specific method.

[0037] [Details of the embodiment of the present disclosure] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0038] Fig. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment of the present disclosure. As illustrated in Fig. 1, a communication system 100 according to an embodiment of the present disclosure has a plurality of nodes. Each node is provided with a communication device according to an embodiment of the present disclosure. Fig. 1 illustrates communication devices 10H, 10G, 10A, and 10B. The communication devices 10H, 10G, 10A, and 10B are, for example, L2 (layer 2) switches, but are not limited thereto.

[0039] In the communication system 100, the multiple nodes are composed of at least one client accommodating node that accommodates client data and at least one aggregation node that aggregates the client data. In the example shown in FIG. 1, the communication devices 10A, 10B, and 10G correspond to the client accommodating nodes, and the communication device 10H corresponds to the aggregation node. In FIG. 1, the communication devices 10A, 10B, and 10G are represented as "client accommodating node A," "client accommodating node B," and "client accommodating node G," respectively, and the communication device 10H is represented as "aggregation node H." In the following description, the communication devices may also be referred to as "nodes."

[0040] A plurality of communication devices (nodes) are connected in a ring shape in accordance with the above-mentioned ITU-T G.8032 ERP. To configure a ring network, each communication device has ports P0 and P1 which are ring ports. To prevent a route loop, a link to be blocked (RPL: Ring Protection Link) is set. For example, as shown in FIG. 1, in normal times, the link between port P0 of a communication device 10H and port P1 of a communication device 10G (client accommodating node G) is blocked. However, the link to be blocked can be set arbitrarily based on the requirements of the communication system 100, etc.

[0041] In order to accommodate client data, each communication device (node) has a client port C0. The client ports C0 of the communication devices 10A, 10B, and 10G are connected to network devices 20A, 20B, and 20G, respectively. For example, the network devices 20A, 20B, and 20G are collective media converters, but are not limited thereto. The collective media converter is connected opposite to a standalone media converter, and the standalone media converter is connected to a client network such as a LAN. In the example shown in FIG. 1, the network devices 31 and 32 correspond to the standalone media converters, and the client network 4 corresponds to the network connected to the standalone media converter.

[0042] The client port C0 of the communication device 10H is connected to a network device 20H, such as a core router or an L3 (layer 3) router. The network device 20H is connected to a wide area network 1 (such as a network such as a data center or a cloud).

[0043] In connection services or access services between bases, an E-LINE configuration with a logical one-to-one (P2P: point-to-point) type connection may be adopted between the client's base and the service provider's center. The same is true in network virtualization or network device distribution, where client data is transferred to a server on the cloud and transfer control processing is performed within the cloud.

[0044] In the embodiment of the present disclosure, the client accommodation node in the communication system 100 configures a one-to-one connection topology by E-LINE by communicating with the aggregation node. When there are multiple aggregation nodes in the communication system 100, the client accommodation node configures a one-to-one connection topology by communicating with any one of the multiple aggregation nodes.

[0045] In the embodiment of the present disclosure, client ports connected to the same aggregation node are grouped into one VLAN (Virtual Local Area Network). A UP MEP (Maintenance association End Point) is set to one of the grouped ports, and a continuity check is performed between two opposing nodes according to Ethernet OAM (Operations, Administration, Maintenance). Specifically, a message (CCM: Continuity Check Message) is periodically transmitted and received between the two opposing nodes. As a result, each node learns the MAC address of the opposing node on either ring port 0 (port P0) or ring port 1 (port P1). Each node holds the learning result of the MAC address as an FDB. The FDB is a database that associates the MAC address of the opposing node with the ring port of the node itself for transmission and reception between the opposing node. In this way, by using a UP MEP in each node (communication device), a CCM frame is transferred via a switch function. Therefore, the MAC address can be learned regardless of which ring port of the communication device the opposing device is connected to. This makes it possible for each communication device to determine the ring port from which the frame should be output.

[0046] Communication on the Ethernet ring between the client accommodation node and the aggregation node is performed by adding a VLAN (Virtual Local Area Network) tag defined by IEEE802.1Q or IEEE802.1ad to the data frame. Also, each node has a table (referred to as a "forwarding table" in this disclosure) for associating an input port (Inport), a trunk (Outport) assigned to the input port, and an output port (Member) for each VLAN ID (VID).

[0047] Therefore, in the embodiment of the present disclosure, the communication system can form a logical path that can identify and transfer a data frame by the VLAN-ID assigned on the Ethernet ring. This logical path realizes a one-to-one connection topology between the aggregation node and the client accommodation node. This logical path is also a logical path that connects a wide area network and a client network. When transferring a data frame on this logical path, it is not necessary to refer to the MAC address of the client included in the data frame. As a result, in the embodiment of the present disclosure, it is possible to transfer frames on a ring network without being limited to a specific method. In the embodiment of the present disclosure, this logical path is called a "service path."

[0048] When forwarding a data frame in a service path, each node does not need to refer to the MAC address of the client contained in the data frame. Therefore, each node is not required to learn the MAC address of the client it accommodates. This makes it possible to prevent the size of the FDB held by each node from becoming large.

[0049] The following describes frame transfer in the communication system 100 shown in Fig. 1. Note that the VID values ​​are examples used to easily explain the embodiments of the present disclosure, and are not intended to limit the embodiments of the present disclosure.

[0050] (1) Transfer from client accommodation node A to aggregation node H The client accommodating node A updates the MAC address learning table (FDB(A)) by learning the MAC address. The client accommodating node A receives data from the client in the form of an Ethernet frame at port C0. Based on the MAC address learning table (FDB(A)) and the forwarding table, the client accommodating node A determines to output the data from port P0, and assigns an S-TAG to the data frame. The value of the SVID (Service provider VLAN ID) included in the S-TAG is a value set according to the client, and is one of 101 to 110 in this example. The client accommodating node A then transmits the data frame from port P0. The frame is transferred to the aggregation node H via nodes on the way.

[0051] (2) Transfer from client accommodation node B to aggregation node H Like client accommodating node A, client accommodating node B updates its MAC address learning table (FDB(B)) by learning the MAC address. Client accommodating node B receives data from a client at port C0. Based on the MAC address learning table (FDB(B)) and the forwarding table, client accommodating node B determines to output this data from port P0, and assigns an S-TAG to the data frame. In this example, the SVID value included in the S-TAG is any one of 201 to 210. Then, client accommodating node B transmits the data frame from port P0.

[0052] A data frame from client accommodating node B is input to port P1 of client accommodating node A. Client accommodating node A determines that the data frame should be forwarded based on the value of the SVID, and outputs the data frame from port P0. Nodes between client accommodating node A and aggregation node H also forward data frames in the same way. Therefore, the data frame is forwarded to aggregation node H.

[0053] (3) Transfer from client accommodation node G to aggregation node H Transfer from client accommodating node G to aggregation node H is basically the same as transfer from client accommodating node A or client accommodating node B to aggregation node H. In addition, in client accommodating node G, the SVID value included in the S-TAG is any one of 301 to 310. Client accommodating node G transmits the data frame from port P0. The data frame is transferred to aggregation node H via nodes on the way.

[0054] (4) Forwarding from aggregation node H to client accommodation nodes A, B, and G Aggregation node H receives a frame at port C0 from the wide area network 1. Aggregation node H refers to the MAC address learning table (FDB(H)) and the forwarding table and determines to forward this data frame to port P0. Aggregation node H then transmits the data frame from port P0.

[0055] Each client accommodating node forwards a frame received at port P0 to client port C0 if the SVID assigned to the frame matches the VLAN ID of the client. On the other hand, if the SVID of the frame does not match the VLAN ID of the client, the client accommodating node relays the data frame by outputting the frame from port P1.

[0056] (5) If a fault occurs on the ring network When a fault occurs on the Ethernet ring, the RPL is unblocked and the FDB is cleared (flushed) in each node. Immediately after that, the CCM frame is flooded (transferred to all ports other than the receiving port). As a result, each node learns a new MAC address and resets the output port. That is, the FDB and forwarding table are updated. That is, a new service path is formed in the communication system 100. The communication system 100 uses this service path to forward frames.

[0057] Fig. 2 is a block diagram for explaining the configuration of a communication device according to an embodiment of the present disclosure. The configuration shown in Fig. 2 is common to the communication devices 10H, 10G, 10A, and 10B. Therefore, in Fig. 2, the communication devices 10H, 10G, 10A, and 10B are collectively referred to as "communication device 10". Note that the communication device according to the embodiment of the present disclosure can function not only as an aggregation node but also as a client accommodation node by setting using hardware or software.

[0058] A communication device 10 according to an embodiment of the present disclosure includes a port P0 (ring port 0), a port P1 (ring port 1), N (N is any integer equal to or greater than 1) client ports C1, C2, ..., Cn, a frame relay unit 50, a continuity monitoring control unit 61, an Ethernet ring control unit 62, and a service path setting unit 63. The frame relay unit 50 includes a VLAN processing unit 51, a control frame processing unit 52, a MAC address learning unit 53, and a service path forwarding unit 54.

[0059] Ports P0 and P1 (ring port 0 and ring port 1) are ports that configure an Ethernet ring by connecting to adjacent ring nodes. Each of client ports C1 to Cn is a port that transmits and receives client signals (client signal 1, client signal 2, . . . client signal N), which are signals for transmitting data frames, and corresponds to client port C0 shown in FIG.

[0060] The frame relay unit 50 functions as a switch that transfers Ethernet frames. More specifically, the VLAN processing unit 51 is responsible for adding a VLAN ID (SVID) to the service path, deleting the VLAN ID, and performing transparency processing for Ethernet frames. The control frame processing unit 52 is responsible for sending and receiving control frames for monitoring continuity and controlling the Ethernet ring. The MAC address learning unit 53 learns the MAC addresses of ring nodes and stores the learned MAC addresses as a MAC address learning table (FDB) 56. The service path forwarding unit 54 is responsible for sending and receiving client signals to and from the client port, and forwards the client signals via the service path connected to the ring port.

[0061] The continuity monitoring control unit 61 transmits and receives Ethernet OAM CCM frames to constantly monitor continuity between adjacent nodes and nodes that terminate service paths. The Ethernet ring control unit 62 controls an Ethernet ring protection function that complies with ITU-T G.8032 ERP. The service path setting unit 63 updates the forwarding table based on the information on continuity from the continuity monitoring control unit 61, the information on topology changes from the Ethernet ring control unit 62, and events of changes in the learning state of the ring node from the MAC address learning unit. Furthermore, the service path setting unit 63 sets the service path forwarding unit 54 according to the updated contents of the forwarding table.

[0062] 3 is a diagram for explaining the addition and deletion of a VLAN tag in the transfer of a data frame according to an embodiment of the present disclosure. As shown in FIG. 3, when the node 10_1 (own node) receives a data frame at any one of the client ports C1 to Cn (for example, the client port C1), the node 10_1 adds a VLAN ID (Outer VID) to the data frame. Then, the node 10_1 transmits the frame onto the ring.

[0063] The schematic structure of a frame is shown in Figure 3. "DA" stands for destination address, "SA" for source address, "DATA" for user data, and "FCS" for frame check sequence. The VLAN tag includes a TPID (tag protocol identifier, "0x88a8" in IEEE802.1ad) and a VID (101 in this example).

[0064] Nodes other than node 10_1 transfer frames different from data frames of the VLAN accommodated in the node between ring ports. Therefore, the data frame is transferred between nodes 10_2 to 10_M and reaches node 10_N, which is an aggregation node. Node 10_N removes the outermost VLAN tag from the data frame received at ring port 0 (port P0). Node 10_N determines a port to output from among ports A1 to Am based on the VLAN-ID of the client data, and transfers the data frame from the determined port.

[0065] 4 is a flowchart for explaining normal operation of a communication system according to an embodiment of the present disclosure. When operation is started, first, in step S11, each node (communication device) sets the MAC address of the opposing service path end node. Next, in step S12, each node starts transmitting a continuity monitoring frame (CCM) to the opposing service path end node. As a result, in step S13, each node receives the continuity monitoring frame.

[0066] In step S14, the MAC address learning unit 53 (see FIG. 2) of the node learns the MAC address based on the continuity monitoring frame, and updates the MAC address learning table (FDB) 56 (see FIG. 2).

[0067] In step S15, the node determines whether the source of the continuity monitoring frame is a service path end node. If the source is a service path end node (YES in step S15), the process proceeds to step S16. On the other hand, if the source is a node other than the service path end node (NO in step S15), the process returns to step S13.

[0068] In step S16, it is determined whether the MAC address of the service path end node is an address newly added to the MAC address learning table. If the MAC address is already registered (NO in step S16), the process proceeds to step S17. On the other hand, if the MAC address of the service path end node is an address newly added to the MAC address learning table (YES in step S16), the process proceeds to step S18.

[0069] In step S17, it is determined whether the receiving port has changed when receiving the continuity monitoring frame from the service path termination node (step S13). If the receiving port has not changed (NO in step S17), the process returns to step S13. In this case, there is no change in the service path. On the other hand, if the receiving port has changed (YES in step S17), the process proceeds to step S18.

[0070] The process after step S18 is for changing the service path (or setting a new service path). In step S18, the node sets or updates a service path in the direction of the receiving port of the continuity monitoring frame. Next, in step S19, the service path setting unit 63 updates the forwarding table and sets a service path for the service path forwarding unit 54 in accordance with the updated contents. After step S19, the process returns to step S13. As a result, a new service path for forwarding the client signal is formed.

[0071] 5 is a flow chart for explaining the operation of a node when the ring configuration is changed. The case where the ring configuration is changed corresponds to, for example, when a fault occurs in the ring network or when the ring network is restored from the fault.

[0072] When a fault occurs or is restored, first, in step S21, any node on the ring network receives a fault occurrence message or a fault recovery notification message. When a node itself detects the occurrence of a fault or the recovery from a fault, the node transmits a fault occurrence message or a fault recovery notification message onto the ring network.

[0073] In step S22, the node that received (or sent) the fault occurrence message or fault recovery notification message determines whether or not it is an owner node that manages the RPL. If it is not an owner node (NO in step S22), the process proceeds to step S23. On the other hand, if it is an owner node (YES in step S22), the process proceeds to step S24, which will be described later.

[0074] In step S23, the RPL is opened or closed. Specifically, when a failure occurs, the RPL is opened. On the other hand, when recovery from the failure occurs, the RPL is closed. Next, the process proceeds to step S24.

[0075] In step S24, the Ethernet ring control unit 62 (see FIG. 2) of the node controls the MAC address learning unit 53 to clear the contents of the MAC address learning table 56. In step S25, the MAC address learning unit 53 clears the contents of the MAC address learning table 56. This also clears the service path settings.

[0076] In step S26, the service path setting unit 63 updates the forwarding table and sets a service path for the service path forwarding unit 54 according to the updated contents. This creates a new service path. When the process of step S26 ends, the process proceeds to the start step of the loop of the normal operation flowchart (step S11 shown in FIG. 4).

[0077] The configuration of the communication system according to the embodiment of the present disclosure is not limited, and various modifications are possible.

[0078] 6 is a diagram illustrating an example of a redundant configuration of a communication system according to an embodiment of the present disclosure. In the communication system 101 according to the embodiment of the present disclosure, a point (1) that aggregates client data can be configured, for example, by node H (communication device 10H) and node G (communication device 10G). Similarly, a point (2) that accommodates client data can be configured, for example, by node A (communication device 10A) and node B (communication device 10B). The configurations of the communication devices 10H, 10G, 10A, and 10B are the same as those shown in FIG. 2, and therefore the following description will not be repeated.

[0079] At base (1), node H may be the active system (shown as "Primary" in FIG. 6) and node G may be the standby system (shown as "Secondary" in FIG. 6). Conversely, node G may be the active system and node H may be the standby system. Each of nodes H and G is physically connected to network device 20H (e.g., a core router). A link aggregation group (LAG) allows the physical links between each node and network device 20H to be treated as one logical link.

[0080] Similarly, at base (2), node A can be the active system and node B can be the standby system (or node B can be the active system and node A can be the standby system). Each of nodes A and B is connected to network device 20A (e.g., an aggregated media converter). By using a Link Aggregation Group (LAG), the physical links between each node and network device 20A can be treated as one logical link.

[0081] Each node designates a peer node and performs continuous continuity checks using CCM. The designated peer nodes are both the active and standby nodes. Therefore, in the example shown in Fig. 6, each of nodes H and G performs continuous continuity checks by sending and receiving CCM messages with both nodes A and B. Meanwhile, each of nodes A and B also performs continuous continuity checks by sending and receiving CCM messages with both nodes H and G using CCM.

[0082] According to this configuration, even if CCM monitoring times out due to a fault such as a failure of an operational node at site (1) or site (2) where the opposing device has a redundant function, the port for forwarding frames can be switched to the standby side. Therefore, frame forwarding can be continued, and communication services can be continued. Note that the embodiment of the present disclosure may include a form in which at least one node on the ring network has a redundant configuration in which the communication device has both an operational system and a standby system. The communication devices may be redundant at all nodes.

[0083] As described above, in the communication system according to the embodiment of the present disclosure, a service path is formed to transfer data. Since each node transfers data using the FDB, there is no need to store the client MAC address. Furthermore, in the communication system according to the embodiment of the present disclosure, data can be transferred without being limited to a specific method.

[0084] For example, in the PBB defined in the above-mentioned IEEE802.1ah, the nodes that make up the PBB network using MAC-in-MAC encapsulation consist of an edge node, the BEB (Backbone Edge Bridge), and a core node, the BCB (Backbone Core Bridge). The edge node that accommodates the client maps the VLAN information of the client data to an I-Tag identifier (I-SID) and sends a frame with a PBB header that uses the MAC address of the node itself as the source address to the backbone network. The edge node also determines the client to which the frame should be forwarded based on the I-Tag identifier that was given to the frame addressed to the node itself from the backbone network. The edge node then removes the PBB header from the frame and forwards it to the relevant client.

[0085] In IEEE802.1ah PBB, two types of VLAN (Virtual Local Area Network) tags, B-Tag and I-Tag, are used for encapsulated MAC frames. This makes it possible to build a large-scale multipoint Layer 2 connection service using Ethernet. The embodiments of the present disclosure are also applicable to such PBB using MAC-in-MAC. In addition, it is possible to eliminate the need to prepare a table independent of the FDB in each node to determine the output destination.

[0086] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims rather than the above-described embodiments, and it is intended to include the equivalent meaning of the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0087] 1. Wide Area Network 4 Client Network 10,10A,10B,10G,10H Communication device 10_1~10_N nodes 20A, 20B, 20G, 20H, 31, 32 Network equipment 50 Frame relay section 51 VLAN processing section 52 Control frame processing unit 53 MAC address learning section 54 Service Path Forwarding Unit 56 MAC Address Learning Table 61 Continuity monitoring control section 62 Ethernet ring control unit 63 Service path setting section 100,101 Communication Systems A, B, G Client accommodation nodes H Aggregation Node S11~S19, S21~S26 steps

Claims

1. The present invention comprises a plurality of communication devices which configure a ring network and establish a one-to-one connection topology with a corresponding device, A link to be blocked is set in the ring network, A communications system in which each of the plurality of communication devices learns the MAC (Media Access Control) address of a counterpart device on the ring network by sending and receiving continuity monitoring frames for monitoring the continuity of the ring network, stores a table that associates the learned MAC addresses with ring ports, and when forwarding a data frame on the ring network, forwards the data frame based on the table without learning the MAC address of the client accommodated.

2. 2. The communication system according to claim 1, wherein each of the plurality of communication devices, when receiving the data frame to be transferred to the opposite device from a client port, assigns a Virtual LAN (VLAN) tag to the data frame, the VLAN tag including a VLAN ID assigned to the client port for communication with the opposite device.

3. 3. The communication system according to claim 2, wherein each of the plurality of communication devices sets a UP MEP (Maintenance association End Point) to one of the client ports belonging to the VLAN ID in order to monitor the continuity of the ring network, and transmits and receives a continuity monitoring frame conforming to Ethernet OAM (Operations, Administration, Maintenance).

4. 4. The communication system according to claim 1, wherein when a fault on the ring network is detected during monitoring of the continuity of the ring network, the blocked link is opened and the plurality of communication devices re-learn the MAC address by sending and receiving a continuity monitoring frame, thereby updating the association between the MAC address and the ring port in the table.

5. At least two of the plurality of communication devices have a redundant configuration including an active system and a standby system; 5. A communication system as claimed in claim 1, wherein when the continuity of the ring network is not possible when the operational system sends or receives a continuity monitoring frame, the data frame is transferred on the ring network based on the table of the standby system.

6. The plurality of communication devices include At least one communication device corresponding to an aggregation node; At least one communication device corresponding to a client accommodation node; 6. The communication system according to claim 1, wherein the aggregation node and the client accommodating node constitute a service path that is a logical path connecting the aggregation node and the client accommodating node.

7. The communication system includes: At least one communication device corresponding to an aggregation node; The communication system according to claim 1 , further comprising: a plurality of communication devices, each of which corresponds to a client accommodation node.

8. A communication device that is provided on a ring network and that establishes a one-to-one connection topology with a counterpart device on the ring network, a monitoring unit that monitors continuity between the ring network and the opposing device by transmitting and receiving a continuity monitoring frame for monitoring continuity of the ring network; a MAC address learning unit that learns a Media Access Control (MAC) address of the opposing device based on a result of the continuity monitoring and stores a table in which the learned MAC address is associated with a ring port; a service path setting unit that sets a service path, which is a logical path connecting the communication device and the opposing device, using the learned MAC address of the opposing device and the ring port; A communication device comprising: a service path forwarding unit that, when forwarding a data frame on the ring network, forwards the data frame in accordance with the service path set by the service path setting unit without learning the MAC address of the client accommodated therein.

9. A communication control method in a ring network configured with a plurality of communication devices that establish a one-to-one connection topology with a corresponding device and in which a blocked link is set, comprising: each of the plurality of communication devices transmitting and receiving a continuity monitoring frame for monitoring continuity of the ring network, thereby learning a MAC (Media Access Control) address of the opposite device; causing each of the plurality of communication devices to update a table associating a MAC address with a ring port with the learned MAC address; and when forwarding a data frame on the ring network based on the table, forwarding the data frame without learning the MAC addresses of clients accommodated by each of the plurality of communication devices.

10. A communication control method for a communication device that is provided on a ring network and that establishes a one-to-one connection topology with a counterpart device on the ring network, comprising: monitoring continuity between the opposite device and the opposite device by transmitting and receiving a continuity monitoring frame; Based on the result of the monitoring of the continuity, the MAC (Media Access Control) address of the opposite device is A step of learning the response; updating a table associating the MAC address with a ring port of the communication device with the learned MAC address; setting a service path which is a logical path connecting the communication device and the opposite device; When forwarding a data frame on the ring network, the data frame is forwarded according to the set service path without learning a MAC address of a client accommodated by the communication device.

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