SWITCH, FRAME RELAY METHOD, AND FRAME RELAY PROGRAM - Patent application

Abstract

The switch (100) includes a plurality of ports including one or more normal ports and one or more redundant ports. The switch receives a communication frame that has arrived at each of the plurality of ports, and if the received communication frame is addressed to a normal port, transmits the received communication frame from the normal port, and if the received communication frame is not addressed to the normal port, transmits the received communication frame from all redundant ports except the receiving port.

Description

[Technical field]

[0001] The present disclosure relates to a switch that relays communication frames. [Background technology]

[0002] In IEEE 802.1CB, which realizes communication redundancy, a switch relays communication frames by duplicating a communication frame sent from a communication device and sending the same communication frame from multiple ports. When the same communication frame is received at multiple ports, the switch relays only the first communication frame received and discards the second and subsequent communication frames received. This realizes communication redundancy in a topology in which multiple routes run in parallel. However, IEEE 802.1CB does not clarify how to set up redundant communication paths.

[0003] Patent Document 1 discloses the following method for setting a communication path: In the method of Patent Document 1, the MAC address of a communication device connected to each port of each switch is registered in each switch. In other words, the method of Patent Document 1 requires that the MAC addresses of all connected communication devices be registered in all switches. Therefore, the method of Patent Document 1 cannot automatically handle a change in MAC address that accompanies replacement of an operating communication device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-011566 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to enable automatic redundant communication even if the MAC address involved in replacing a communication device during operation is not known. [Means for solving the problem]

[0006] The switch of the present disclosure comprises: A switch that relays communication frames communicated between a plurality of communication devices, A plurality of ports including one or more normal ports and one or more redundant ports; a receiving unit that receives a communication frame that has arrived at each of the plurality of ports; a transmitting unit that transmits a received communication frame from a normal port when the received communication frame is a frame addressed to a normal port, and transmits the received communication frame from all redundant ports except a receiving port when the received communication frame is not a frame addressed to the normal port; Equipped with. Effect of the Invention

[0007] According to the present disclosure, it is possible to automatically perform redundant communication even if the MAC address associated with replacement of an operating communication device is not known. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 shows an example of the configuration of a communication system 200 according to a first embodiment. [Diagram 2] FIG. 2 shows an example of the configuration of the switch 100 according to the first embodiment. [Diagram 3] FIG. 2 shows an example of the configuration of a communication device 210 according to the first embodiment. [Figure 4] 3 is a flowchart of a frame relay method according to the first embodiment. [Diagram 5] 3 is a flowchart of a frame relay method according to the first embodiment. [Figure 6] FIG. 1 is a diagram illustrating non-redundancy in MAC address learning. [Figure 7]11 is a flowchart of a frame relay method according to the second embodiment. [Figure 8] 13 is a flowchart of a frame relay method in the third embodiment. [Figure 9] 13 is a flowchart of the operation of the communication device 210 according to the fourth embodiment. [Figure 10] FIG. 1 shows an example of the configuration of a communication system 200 according to a first embodiment. [Figure 11] FIG. 1 shows an example of the configuration of a communication system 200 according to a first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In the embodiments and drawings, the same or corresponding elements are denoted by the same reference numerals. Descriptions of elements denoted by the same reference numerals as those of elements described above will be omitted or simplified as appropriate. Arrows in the drawings primarily indicate data flow or processing flow.

[0010] Embodiment 1 A switch 100 that relays communication frames will be described with reference to FIGS.

[0011] ***Configuration Description*** The configuration of a communication system 200 will be described with reference to FIG. The communication system 200 includes a plurality of communication devices 210 and a plurality of switches 100 . A plurality of communication devices 210 and a plurality of switches 100 form a network.

[0012] Each communication device 210 is connected to one of the switches 100 using a communication cable. The multiple switches 100 are connected to each other using communication cables. The communication cable constitutes a communication path between the communication device 210 and the switch 100 or a communication path between two switches 100 .

[0013] A plurality of communication devices 210 transmit and receive communication frames to and from each other via one or more switches 100 . Each switch 100 relays communication frames communicated among a plurality of communication devices 210. The switch 100 is also called a relay device.

[0014] The configuration of the switch 100 will be described with reference to FIG. The switch 100 includes a processing circuit 101 and a plurality of ports 102 . The processing circuit 101 and the multiple ports 102 are connected via signal lines.

[0015] 2, the switch 100 has three ports 102. However, the switch 100 may have two ports 102 or four or more ports 102.

[0016] The processing circuit 101 includes elements such as a receiving unit 111, a transmitting unit 112, and a memory unit 120.

[0017] The processing circuit 101 is hardware that realizes a receiving unit 111 , a transmitting unit 112 , and a memory unit 120 . The processing circuitry 101 may be dedicated hardware, or may be a processor that executes a program stored in a memory.

[0018] When the processing circuitry 101 is dedicated hardware, the processing circuitry 101 may be, for example, a single circuit, a multiple circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field Programmable Gate Array.

[0019] When the processing circuitry 101 is a processor that executes programs stored in a memory, the processing circuitry 101 constitutes a computer. The receiving unit 111 and the transmitting unit 112 can be realized by software. A program for causing a computer to function as the receiving unit 111 and the transmitting unit 112 is called a frame relay program. The frame relay program is stored in the memory and executed by the processor. The frame relay program can be recorded (stored) in a computer-readable manner on a non-volatile recording medium such as an optical disk or a flash memory.

[0020] The storage unit 120 can be realized by a memory. The storage unit 120 stores an address table 121 and the like. The address table 121 will be described later.

[0021] The configuration of the communication device 210 will be described with reference to FIG. The communication device 210 includes a processing circuit 211 and a port 214 . The processing circuit 211 and the port 214 are connected via a signal line.

[0022] The processing circuit 211 includes elements such as a transmitting unit 212 and a receiving unit 213 .

[0023] The processing circuit 211 is hardware that realizes a transmitting unit 212 and a receiving unit 213 . The processing circuitry 211 may be dedicated hardware, or may be a processor that executes a program stored in a memory.

[0024] ***Explanation of Operation*** The operation procedure of the switch 100 corresponds to a frame relay method, and also corresponds to a processing procedure according to a frame relay program. The frame relay method will be described below.

[0025] Based on FIG. 1, the multiple ports 102 of the processing circuit 101 will be described. The multiple ports 102 are classified into normal ports and redundant ports. In Fig. 1, solid arrows indicate the flow of communication frames transmitted from normal ports, and dashed arrows indicate the flow of communication frames transmitted from redundant ports. A normal port is a port 102 that is connected through a single path to a communication device 210 that has no alternative path between itself and the switch 100 and among the multiple communication devices 210 . For example, a communication device (A1) is connected to a switch (A) through one communication path. In other words, there is no alternative path between the communication device (A1) and the switch (A). Therefore, among the multiple ports 102 of the switch (A), the port 102 to which the communication device (A1) is connected is a normal port. Similarly, among the multiple ports 102 of the switch (A), the port 102 to which the communication device (A2) is connected is a normal port. A redundant port is a port that is not a normal port. Specifically, a redundant port is a port 102 that is connected to a communication device 210, among multiple communication devices 210, that has an alternative path between the communication device 210 and the switch 100, through multiple paths. For example, among the multiple ports 102 of the switch (A), three ports 102 that are neither a normal port to which a communication device (A1) is connected nor a normal port to which a communication device (A2) is connected are redundant ports. Each of the six communication devices (B1, B2, C1, C2, D1, D2) is connected to the switch (A) through two or more communication paths. In other words, between each of the six communication devices (B1, B2, C1, C2, D1, D2) and the switch (A), there is an alternative communication path via one or more switches 100. In each switch 100, a number of ports 102 are classified into normal ports and redundant ports according to a user setting.

[0026] The communication frame will now be described. A source address, a destination address, and a sequence number are set in a communication frame. The source address is the address of the communication device 210 that is the source of the communication frame. The destination address is the address of the communication device 210 that is the destination of the communication frame. A MAC address is used as the address of the communication device 210. MAC is an abbreviation for Media Access Control.

[0027] The communication device 210 will now be described. The transmitter 212 of the source communication device 210 transmits the communication frame from a port 214 . The transmitted communication frame passes through one or more switches 100 and arrives at the destination communication device 210 . The receiving unit 213 of the destination communication device 210 receives the communication frame that has arrived at the port 214 .

[0028] The frame relay method will be described with reference to FIGS. Steps S101 to S113 are executed in each switch 100 every time a communication frame arrives at any one of the ports 102 of the switch 100. The port 102 through which the communication frame arrives is called the receiving port.

[0029] In step S101, the receiving unit 111 receives a communication frame that has arrived at a receiving port. A received communication frame is referred to as a received frame.

[0030] In step S102, the receiving unit 111 determines whether the receiving port is a normal port or a redundant port.

[0031] For example, the receiver 111 makes the determination by referring to a port table. The port table indicates the type of port 102 (normal port or redundant port) for each port 102. Specifically, the port table indicates the port type in association with the port identifier for each port 102. The port table is created by a user and stored in advance in the storage unit 120. The receiver 111 refers to the port table and determines whether the port type associated with the port identifier of the receiving port is a normal port or a redundant port.

[0032] If the receiving port is a normal port, the process proceeds to step S103. If the receiving port is a redundant port, the process proceeds to step S105.

[0033] In step S 103 , the receiving unit 111 determines whether the source address of the received frame is registered in the address table 121 .

[0034] The address of the communication device 210 connected to each normal port is registered in the address table 121. Specifically, the address table 121 registers the address of the communication device 210 in association with the port identifier for each normal port. The receiving unit 111 determines whether an address identical to the source address set in the received frame is registered in the address table 121 in association with the port identifier of the receiving port.

[0035] If the source address of the received frame is registered in the address table 121, the process proceeds to step S106. If the source address of the received frame is not registered in the address table 121, the process proceeds to step S104.

[0036] In step S104, the receiving unit 111 registers the source address of the received frame in the address table 121 in association with the receiving port.

[0037] Specifically, the receiver 111 registers the source address of the received frame in the address table 121 in association with the port identifier of the receiving port.

[0038] In step S105, the receiving unit 111 determines whether or not a communication frame identical to the received frame has already been received.

[0039] A communication frame that is the same as the received frame is a communication frame that has arrived at one of the redundant ports of the switch 100 via a communication path different from the communication path of the received frame before arriving at the receiving port of the switch 100. A set of a source address, a destination address, and a sequence number set in the same communication frame as the received frame matches a set of a source address, a destination address, and a sequence number set in the received frame.

[0040] For example, the receiving unit 111 makes the determination by referring to the communication table. In the communication table, a sequence number is registered in association with each source address. When a communication frame is received, the receiver 111 searches the communication table for a sequence number associated with the same source address as the source address set in the received communication frame. If the found sequence number is smaller than the sequence number set in the received communication frame, the receiver 111 updates the found sequence number to the sequence number set in the received communication frame. The receiving unit 111 searches the communication table for a sequence number associated with the same source address as the source address set in the received frame. If the found sequence number is equal to or greater than the sequence number set in the received frame, the receiving unit 111 determines that the same communication frame as the received frame has already been received. Alternatively, the receiving unit 111 may refer to the communication table and make the determination as follows. In the communication table, a sequence number is registered in association with each source address. When a communication frame is received, the receiver 111 searches the communication table for a sequence number associated with the same source address as the source address set in the received communication frame. If the receiver 111 cannot find the sequence number set in the received communication frame, the receiver 111 registers the sequence number set in the received communication frame. If the receiver 111 finds the sequence number set in the received communication frame, the receiver 111 determines that the same communication frame as the received frame has already been received.

[0041] If a communication frame identical to the received frame has already been received, the received frame is not relayed because the same communication frame as the received frame has already been relayed, and the process ends.

[0042] If a communication frame identical to the received frame has not been received, the process proceeds to step S106.

[0043] In step S 106 , the receiver 111 passes the received frame and the receiving port identifier to the transmitter 112 .

[0044] After step S106, the process proceeds to step S111.

[0045] In step S 111 , the transmitting unit 112 determines whether the destination address of the received frame is registered in the address table 121 .

[0046] Specifically, the transmitting unit 112 determines whether the same address as the destination address set in the received frame is registered in the address table 121.

[0047] If the destination address of the received frame is registered in the address table 121, the process proceeds to step S112. If the destination address of the received frame is not registered in the address table 121, the process proceeds to step S113.

[0048] In step S112, the transmitting unit 112 transmits the received frame from the corresponding port, whereby the received frame is relayed.

[0049] The corresponding port is a normal port to which the communication device 210 that is the destination of the received frame is connected.

[0050] The relevant port is determined by using the address table 121. The transmitting unit 112 refers to the address table 121 and determines that the normal port corresponding to the destination address of the received frame is the corresponding port. Specifically, the transmitting unit 112 finds a port identifier associated with the same address as the destination address set in the received frame from the address table 121. The port 102 identified by the found port identifier is the corresponding port.

[0051] After step S112, the process ends.

[0052] In step S113, the transmitting unit 112 transmits the received frame from all redundant ports except the receiving port, thereby relaying the received frame.

[0053] Received frames are duplicated and then transmitted.

[0054] The redundant port is determined, for example, by using a port table.

[0055] After step S113, the process ends.

[0056] ***Advantages of the First Embodiment*** The method of Patent Document 1 cannot automatically accommodate changes in MAC addresses that accompany replacement of communication devices. One method for dealing with MAC address changes is MAC address learning, which is a function that registers the correspondence between the source MAC address of a received communication frame and the receiving port, and then transmits the communication frame from the port corresponding to the MAC address that matches the destination MAC address of the received communication frame. However, using MAC address learning makes it impossible to achieve redundancy as follows: 6, in order to achieve redundancy in communication from communication device (3) to communication device (1), it is desirable to be able to use the communication path indicated by the dashed arrow, for example. However, due to MAC address learning, only the communication path indicated by the double arrow can be used.

[0057] On the other hand, the first embodiment has the following features. In the target network, a switch port that connects a section where there is no alternative route is defined as a normal port, and a switch port that connects a section where there is an alternative route is defined as a redundant port. The switch uses the MAC address learning function to register only the MAC address of the communication device connected to the normal port. When a communication frame destined for an unregistered MAC address is received, the switch relays the frame using all redundant ports except for the receiving port.

[0058] The features of the first embodiment are as follows. Each switch normally registers the MAC address of the communication device connected to the other end of its port using MAC address learning, and relays and transmits the data as described below in 1) and 2). 1) If the communication device with the destination address of the received communication frame is not connected to any of the normal ports of the switch, the received communication frame is duplicated and relayed using all redundant ports other than the receiving port. 2) If the communication device with the destination address of the received communication frame is connected to a normal port of the switch itself, the frame is relayed using only that normal port.

[0059] The first embodiment provides the following advantages. The switch uses the MAC address learning function to register only the MAC addresses of the communication devices connected to the normal port, and determines that unregistered MAC addresses are connected to the redundant port. This makes it possible to automatically respond to changes in MAC addresses that occur when communication devices are replaced during operation. The switch relays communication frames addressed to unregistered MAC addresses using all redundant ports except the receiving port, thereby achieving communication redundancy.

[0060] Embodiment 2 The embodiment in which the address table 121 is created in advance will be described with reference to FIG. 7, mainly with respect to the points that differ from the first embodiment.

[0061] ***Configuration Description*** The configurations of the communication system 200, the switch 100, and the communication device 210 are the same as those in the first embodiment.

[0062] ***Explanation of Operation*** The address table 121 is created by a user and stored in advance in the storage unit 120 of the switch 100 .

[0063] The frame relay method will be described with reference to FIG. In step S101, the receiving unit 111 receives a communication frame that has arrived at a receiving port. Step S101 is as described in the first embodiment.

[0064] After step S101, the process proceeds to step S201.

[0065] In step S201, the receiving unit 111 determines whether the receiving port is a normal port or a redundant port. The determination method is the same as that in step S102 in the first embodiment.

[0066] If the receiving port is a normal port, the process proceeds to step S106. If the receiving port is a redundant port, the process proceeds to step S105.

[0067] Steps S105, S106, and the subsequent steps are the same as those in the first embodiment.

[0068] ***Effects of the second embodiment*** In the first embodiment, when creating an address table by MAC address learning, the communication device connected to the normal port needs to communicate at least once. Until the MAC address is registered by MAC address learning, the communication device connected to the normal port cannot relay a communication frame addressed to the communication device.

[0069] The second embodiment has the following features. The MAC addresses of the communication devices connected to the normal ports are registered in the address table 121 by the user, not by MAC address learning.

[0070] The detailed features of the second embodiment are as follows. The MAC address of the communication device connected to the normal port is registered by the user, and each switch relays and transmits the following 1) and 2). 1) If the communication device with the destination address of the received communication frame is not connected to any of the normal ports of the switch, the received communication frame is duplicated and relayed using all redundant ports other than the receiving port. 2) If the communication device with the destination address of the received communication frame is connected to a normal port of the switch itself, the frame is relayed using only that normal port.

[0071] The second embodiment provides the following advantages. Even before a communication device connected to a normal port performs communication, the switch can correctly perform relay transmission to that communication device.

[0072] Embodiment 3 A form that enables relaying of communication frames addressed to an uncommunicated communication device 210 connected to a normal port even if an address table 121 is not created in advance will be described with reference to FIG. 8, mainly with respect to the differences from embodiment 1.

[0073] ***Configuration Description*** The configurations of the communication system 200, the switch 100, and the communication device 210 are the same as those in the first embodiment.

[0074] ***Explanation of Operation*** The frame relay method will be described with reference to FIG. Steps S101 to S106 are the same as those described in the first embodiment. After step S106, the process proceeds to step S301.

[0075] In step S301, the transmitting unit 112 determines whether the destination address of the received frame is registered in the address table 121. The determination method is the same as that in step S111 in the first embodiment.

[0076] If the destination address of the received frame is registered in the address table 121, the process proceeds to step S112. If the destination address of the received frame is not registered in the address table 121, the process proceeds to step S302.

[0077] In step S112, the transmitting unit 112 transmits the received frame from the corresponding port, whereby the received frame is relayed. Step S112 is as described in the first embodiment.

[0078] In step S302, the transmitting unit 112 transmits the received frame from all redundant ports except the receiving port. Furthermore, the transmitter 112 transmits the received frame from all normal ports except the receiving port. This allows the received frame to be relayed.

[0079] ***Effects of the Third Embodiment*** In the first embodiment, when creating an address table by MAC address learning, the communication device connected to the normal port needs to communicate at least once. Until the MAC address is registered by MAC address learning, the communication device connected to the normal port cannot relay a communication frame addressed to the communication device.

[0080] The third embodiment has the following features. The switch relays communication frames whose destination address is an unregistered MAC address using not only redundant ports but also normal ports.

[0081] The detailed features of the third embodiment are as follows. Each switch normally registers the MAC address of the communication device connected to the other end of its port using MAC address learning, and relays and transmits the data as described below in 1) and 2). 1) If the communication device with the destination address of the received communication frame is not connected to any of the normal ports of the switch, the received communication frame is duplicated and relayed using all redundant ports and normal ports other than the receiving port. 2) If the communication device with the destination address of the received communication frame is connected to a normal port of the switch itself, the frame is relayed using only that normal port.

[0082] The third embodiment provides the following advantages. Even before a communication device connected to a normal port performs communication, the switch can correctly perform relay transmission to that communication device.

[0083] Embodiment 4 A mode in which the address of the communication device 210 connected to the normal port can be registered in advance in the address table 121 will be described with reference to FIG. 9, mainly with respect to the points that differ from the first embodiment.

[0084] ***Configuration Description*** The configurations of the communication system 200, the switch 100, and the communication device 210 are the same as those in the first embodiment.

[0085] ***Explanation of Operation*** The operation of the communication device 210 will be described with reference to FIG. In step S401, the port 214 detects a connection to the network of the communication system 200.

[0086] For example, a connection to the network of the communication system 200 is detected as follows. A user connects one end of a communication cable to a normal port of the switch 100 and connects the other end of the communication cable to the port 214 of the communication device 210 . The port 214 of the communication device 210 detects the connection of the communication cable.

[0087] In step S 402 , the transmitting unit 212 creates a communication frame for the entire network of the communication system 200 , and transmits the created communication frame from the port 214 .

[0088] A communication frame addressed to the entire network of the communication system 200 is a communication frame addressed to all communication devices 210 and reaches all communication devices 210 . For example, when the network of the communication system 200 is an Ethernet, the transmission unit 212 transmits a communication frame in which a broadcast address is set as the destination address.

[0089] A communication frame to the entire network of the communication system 200 is relayed by one or more switches 100 and reaches all communication devices 210 except for the source communication device 210.

[0090] When a communication frame for the entire network of the communication system 200 arrives at the port 102, the switch 100 executes the frame relay method in the same manner as when a normal communication frame arrives. If the receiving port is a normal port, the address of the source communication device 210 is registered in the address table 121 in association with the normal port that is the receiving port (step S104).

[0091] ***Effects of the fourth embodiment*** In the first embodiment, when creating an address table by MAC address learning, the communication device connected to the normal port needs to communicate at least once. Until the MAC address is registered by MAC address learning, the communication device does not relay communication frames addressed to the communication device connected to the normal port.

[0092] The fourth embodiment has the following features. Each communication device performs a single communication that reaches the entire network when a port is connected.

[0093] The detailed features of the fourth embodiment are as follows. Each communication device performs a single communication that reaches the entire network when a port is connected. Each switch normally registers the MAC address of the communication device connected to the other end of its port using MAC address learning, and relays and transmits the data as described below in 1) and 2). 1) If the communication device with the destination address of the received communication frame is not connected to any of the normal ports of the switch, the received communication frame is duplicated and relayed using all redundant ports other than the receiving port. 2) If the communication device with the destination address of the received communication frame is connected to a normal port of the switch itself, the frame is relayed using only that normal port.

[0094] The fourth embodiment has the following advantages. Relay transmission to the communication device can be performed correctly.

[0095] ***Supplementary explanation of implementation form*** A supplementary explanation of normal ports will be given based on FIG. 10 and FIG. The normal ports include ports that are connected to adjacent communication devices 210 via a single path, as well as ports that are connected to adjacent switches 100 via a single path. In Figure 10, the right port of switch (B) has an alternative path between it and switches (F, G, H, I). However, the right port of switch (B) does not have an alternative path between it and switch (E). Therefore, the right port of switch (B) is a normal port in relation to switch (E). The right port of the switch (B) is a port (normal port) that is connected to the communication device (E1) that has no alternative path between it and the switch (B) via a single path (B→E→E1). In Figure 11, there is an alternative route between the right port of switch (B) and switch (E). For example, in addition to route (B → E), there is route (B → C → I → F → E). Therefore, the right port of switch (B) is a redundant port, not a normal port. In addition, the right port of switch (B) is a port (redundant port) that is connected to communication device (E1) that has an alternative route between it and switch (B) via multiple routes (B→E→E1, B→C→I→F→E→E1, etc.).

[0096] Each embodiment is an example of a preferred embodiment, and is not intended to limit the technical scope of the present disclosure. Each embodiment may be implemented in part or in combination with other embodiments. The procedures described using flow charts, etc. may be modified as appropriate.

[0097] Each element of the switch 100 and the communication device 210 may be implemented in software, hardware, firmware, or a combination of these. The "part" of each element of the switch 100 and the communication device 210 may be interpreted as a "process," a "step," a "circuit," or a "circuitry."

[0098] In the embodiment, a switch that relays communication frames communicated between a plurality of communication devices has been disclosed. The switch is A plurality of ports are classified into normal ports that are connected through a single path to a communication device among the plurality of communication devices that has no alternative path between the communication device and the switch, and redundant ports that are ports other than normal ports; a receiving unit that receives a communication frame that has arrived at each of the plurality of ports; a transmitting unit which determines whether a destination address of a received communication frame is registered in an address table in which addresses of communication devices connected to the normal ports are registered for each normal port, and transmits the received communication frame from a normal port corresponding to the destination address if the destination address is registered in the address table, and transmits the received communication frame from all redundant ports except for a receiving port through which the received communication frame arrived if the destination address is not registered in the address table; Equipped with.

[0099] The receiving unit determines whether the receiving port is a normal port and the source address of the received communication frame is registered in the address table, and if the receiving port is a normal port and the source address is not registered in the address table, it registers the source address in the address table in correspondence with the receiving port.

[0100] When the destination address is not registered in the address table, the transmitting unit transmits the received communication frame from all redundant ports except the receiving port and from all normal ports except the receiving port.

[0101] a communication device connected to a normal port of the switch among the plurality of communication devices transmits a communication frame that reaches all of the plurality of communication devices except for the communication device itself when the communication device is connected to the normal port of the switch; The receiving unit receives a communication frame that has arrived at the normal port, and registers a source address of the received communication frame in the address table in association with the normal port. [Explanation of symbols]

[0102] 100 switch, 101 processing circuit, 102 port, 111 receiving unit, 112 transmitting unit, 120 storage unit, 121 address table, 200 communication system, 210 communication device, 211 processing circuit, 212 transmitting unit, 213 receiving unit, 214 port.

Claims

1. a switch that relays communication frames communicated between a plurality of communication devices, a plurality of ports that are memorized as being normal ports or redundant ports; a receiving unit that receives communication frames that have arrived at each of the plurality of ports; a transmitting unit that transmits a received communication frame from a normal port when the received communication frame is a frame addressed to a normal port, and transmits the received communication frame from all redundant ports except a receiving port when the received communication frame is not a frame addressed to the normal port; A switch comprising:

2. A port to which a communication device is connected is set as a normal port, and a port other than the port to which the communication device is connected is set as a redundant port. The switch of claim 1 .

3. The normal port is connected through a single path for which no alternative path exists; The redundant port is a port other than the normal port. The switch of claim 1 .

4. The transmitter stores the address of the communication device connected to the normal port. The switch of claim 1 .

5. The receiving unit stores the source address of the communication frame that has arrived at the normal port in association with the normal port. The switch of claim 1 .

6. A frame relay method using a switch that relays communication frames communicated between a plurality of communication devices, The switch is a plurality of ports memorizing whether they are normal ports or redundant ports; receiving a communication frame that has arrived at each of the plurality of ports; A frame relay method for transmitting a received communication frame from a normal port if the received communication frame is a frame addressed to a normal port, and transmitting the received communication frame from all redundant ports except the receiving port if the received communication frame is not a frame addressed to the normal port.

7. A frame relay program for causing a switch that relays communication frames communicated between a plurality of communication devices to execute reception processing and transmission processing, the switch includes a plurality of ports each stored as a normal port or a redundant port; The receiving process receives a communication frame that has arrived at each of the plurality of ports, The transmission process is a frame relay program that transmits the received communication frame from the normal port if the received communication frame is a frame addressed to a normal port, and transmits the received communication frame from all redundant ports except the receiving port if the received communication frame is not a frame addressed to the normal port.

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