Relay device

Abstract

To implement the function of giving an appropriate response to a specific request by small-sized software.SOLUTION: A relay device 2 relays communication frames between first and second ECUs 3 and 4 connected to first and second communication lines 5 and 6, respectively. The relay device 2 includes an L3 switch 12, a control unit 21, and a RAM 33. The L3 switch 12 executes a relay process for relaying the communication frames. The control unit 21 controls the relay device 2. The RAM 33 stores a fixed message 35. The L3 switch 12 determines whether or not a communication frame satisfying a request detection condition (hereinafter, a specific frame) has been received from the first and second ECUs 3 and 4. When the specific frame has been received, the control unit 21 transmits a communication frame including the fixed message 35.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a relay device that relays communication frames between a plurality of communication devices.

Background Art

[0002] Patent Document 1 describes that a network switch to which a plurality of communication lines are connected and which relays data between the plurality of communication lines is configured to rewrite at least one of an address resolution table and permission information in response to an external command output from an external device. The network switch is configured to relay data using address information set to be available in the permission information. The address resolution table records a plurality of pieces of address information for identifying individual communication devices with each other in a plurality of protocols. The permission information is included in the address resolution table and indicates whether the address information can be used for each of the plurality of pieces of address information.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a result of the inventors' detailed examination, the following problems were found. In a network switch realized by hardware, an appropriate response may not be possible for a specific request received from an external device. Further, when attempting to realize a function of making an appropriate response to a specific request received from an external device by software, it may not be possible to implement it with small-scale software.

[0005] An object of the present disclosure is to realize a function of making an appropriate response to a specific request with small-scale software.

Means for Solving the Problems

[0006] One aspect of the present disclosure is a relay device (2) configured to relay communication frames between a plurality of communication lines (5, 6) and a plurality of communication devices (3, 4) connected to each of the plurality of communication lines.

[0007] The relay device of the present disclosure includes a relay processing execution unit (12), a control unit (21), and a message storage unit (33). The relay processing execution unit is configured to execute a relay process for relaying communication frames.

[0008] The control unit is configured to control the relay device. The message storage unit is configured to store a preset fixed message (35). The relay processing execution unit includes specific frame detection units (S10, S30, S35). The specific frame detection units are configured to determine whether a specific frame, which is a specific communication frame, has been received from a communication device.

[0009] The control unit includes fixed frame transmission units (S110 to S140, S210 to S220). The fixed frame transmission units are configured to transmit a fixed frame, which is a communication frame including a fixed message, when the specific frame detection unit determines that a specific frame has been received.

[0010] In the relay device of the present disclosure configured as described above, even when the relay processing execution unit is configured as hardware, the relay processing execution unit performs a simple process of determining whether a specific frame has been received, and the control unit performs a process of transmitting a fixed frame corresponding to the specific frame. Thereby, the relay device of the present disclosure can realize a function of appropriately responding to a specific request.

[0011] Furthermore, in the relay device of the present disclosure, the control unit transmits a fixed frame, which is a communication frame including a fixed message preset in the message storage unit, as a response corresponding to a specific frame. Thereby, the relay device of the present disclosure can realize the process of transmitting the fixed frame with small-scale software.

[0012] As described above, the relay device of the present disclosure can realize the function of making an appropriate response to a specific request with small-scale software.

Brief Description of Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0014] [First Embodiment] The first embodiment of the present disclosure will be described below with reference to the drawings. As shown in FIG. 1, the communication system 1 of this embodiment includes a relay device 2, a first ECU 3, and a second ECU 4. ECU is an abbreviation for Electronic Control Unit.

[0015] The relay device 2 includes an MPU 11 and an L3 switch 12. MPU is an abbreviation for Micro Processing Unit. The MPU 11 includes a control unit 21, an Ethernet communication unit 22, an SPI communication unit 23, and a storage unit 24. Ethernet is a registered trademark. SPI is an abbreviation for Serial Peripheral Interface.

[0016] The control unit 21 is an electronic control device mainly composed of a microcomputer including a CPU 31, a ROM 32, a RAM 33, etc. Various functions of the microcomputer are realized by the CPU 31 executing a program stored in a non-transitory tangible recording medium. In this example, the ROM 32 corresponds to the non-transitory tangible recording medium storing the program. Also, by executing this program, a method corresponding to the program is executed. Note that part or all of the functions executed by the CPU 31 may be configured hardware-wise by one or a plurality of ICs, etc. Also, the number of microcomputers constituting the control unit 21 may be one or plural. The RAM 33 stores a fixed message 35 described later.

[0017] The Ethernet communication unit 22 communicates with the L3 switch 12 according to the Ethernet protocol. The SPI communication unit 23 communicates with the L3 switch 12 according to the SPI protocol.

[0018] The storage unit 24 is a storage device for storing various data. The L3 switch 12 is a network switch having a function of relaying communication between the first ECU 3 and the second ECU 4 according to the Ethernet protocol. The L3 switch 12 is configured as hardware including a circuit such as an FPGA, for example. FPGA is an abbreviation for Field Programmable Gate Array.

[0019] The L3 switch 12 and the first ECU 3 are connected to be capable of data communication with each other via the first communication line 5. The L3 switch 12 and the second ECU 4 are connected to be capable of data communication with each other via the second communication line 6.

[0020] Next, an explanation will be given of the mechanism by which the L3 switch 12 relays communication frames. As shown in FIG. 2, the IP address of the first ECU 3 is "192.168.10.10", and the IP address of the second ECU 4 is "192.168.20.10".

[0021] The MAC address of the first ECU 3 is "66-55-00-33-AA-A1", and the MAC address of the second ECU 4 is "66-55-00-33-AA-A2". Hereinafter, the MAC address of the first ECU 3 will also be denoted as "MAC-A", and the MAC address of the second ECU 4 will also be denoted as "MAC-B".

[0022] The MAC address of the L3 switch 12 is "66-55-00-33-AA-01". The first ECU 3 is connected to the first port 41 of the L3 switch 12 via the first communication line 5. The second ECU 4 is connected to the second port 42 of the L3 switch 12 via the second communication line 6.

[0023] The VLAN_ID of the first port 41 is "10", and the VLAN_ID of the second port 42 is "20". The VLAN_ID is a number for identifying a plurality of virtual LANs (hereinafter, VLANs) formed by virtually dividing a LAN. VLAN is an abbreviation for Virtual Local Area Network. Hereinafter, the VLAN_ID will also be referred to as VID.

[0024] The L3 switch 12 includes a VLAN (hereinafter, the first VLAN) with a VLAN_ID set to "10" and a VLAN (hereinafter, the second VLAN) with a VLAN_ID set to "20".

[0025] The IP address of the first VLAN is "192.168.10.1", and the subnet address of the first VLAN is "192.168.10.0 / 24". The IP address of the second VLAN is "192.168.20.1", and the subnet address of the first VLAN is "192.168.20.0 / 24".

[0026] As shown by arrow L1, the first ECU 3 transmits a communication frame addressed to the second ECU 4 to the first port 41 of the L3 switch 12. The communication frame includes an Ethernet header and an IP header.

[0027] The type of communication frame transmitted by the first ECU 3 and the second ECU 4 is "IPv4". Hereinafter, the communication frame transmitted by the first ECU 3 and the second ECU 4 is also referred to as an IPv4 frame.

[0028] The IPv4 frame includes a destination MAC address (hereinafter, D-MAC) area, a source MAC address (hereinafter, S-MAC) area, a destination IP address (hereinafter, D-IP) area, and a source IP address (hereinafter, S-IP) area.

[0029] The D-MAC area and the S-MAC area are included in the Ethernet header. The D-IP area and the S-IP area are included in the IP header. The MAC address of the L3 switch 12 is stored in the D-MAC area of the IPv4 frame transmitted by the first ECU 3 to the L3 switch 12.

[0030] The MAC address of the first ECU 3 is stored in the S-MAC area of the IPv4 frame transmitted by the first ECU 3 to the L3 switch 12. The IP address of the second ECU 4 is stored in the D-IP area of the IPv4 frame transmitted by the first ECU 3 to the L3 switch 12.

[0031] The IP address of the first ECU 3 is stored in the S-IP area of the IPv4 frame transmitted by the first ECU 3 to the L3 switch 12. The L3 switch 12 includes a routing table 43 and an ARP table 44. ARP is the abbreviation of Address Resolution Protocol.

[0032] The routing table 43 sets the correspondence between the subnet address, the VLAN_ID, and the IP address of the destination device. The ARP table 44 sets the correspondence between the IP address and the MAC address.

[0033] For example, when a device belonging to the subnet address specified by "192.168.10.0 / 24" is the destination, the routing table 43 indicates that it is to be transferred to a device directly connected to the VLAN specified by "10" (i.e., the first VLAN).

[0034] For example, when a device belonging to the subnet address specified by "192.168.20.0 / 24" is the destination, the routing table 43 indicates that it is to be transferred to a device directly connected to the VLAN specified by "20" (i.e., the second VLAN).

[0035] For example, when a device belonging to the subnet address specified by "192.168.30.0 / 24" is the destination, the routing table 43 indicates that it is to be transferred to a device connected to the VLAN specified by "20" (i.e., the second VLAN) and specified by the IP address "192.168.20.2".

[0036] For example, when the destination is unknown, the routing table 43 indicates that it is to be transferred to a device connected to the VLAN specified by "30" and specified by the IP address "10.10.XXX.X".

[0037] For example, the ARP table 44 indicates that the MAC address of the device specified by "192.168.10.10" (i.e., the first ECU 3) is "66-55-00-33-AA-A1".

[0038] The ARP table 44 indicates, for example, that the MAC address of the device specified by "192.168.20.10" (i.e., the second ECU 4) is "66-55-00-33-AA-A2".

[0039] When the L3 switch 12 acquires the above IPv4 frame from the first ECU 3, as shown in process P1, it determines that it may transfer the IPv4 frame to the VLAN specified by "20" (i.e., the second port 42) by referring to the routing table 43.

[0040] Furthermore, as shown in process P2, the L3 switch 12 refers to the ARP table 44 to identify the MAC address of the device that is the destination of the acquired IPv4 frame.

[0041] As shown by the arrow L2, the L3 switch 12 transfers the IPv4 frame to the second ECU 4 by transmitting the IPv4 frame from the second port 42. The IPv4 frame that the L3 switch 12 transfers to the second ECU 4 includes a D-MAC area, an S-MAC area, a VID area, a D-IP area, and an S-IP area.

[0042] The D-MAC area, the S-MAC area, and the VID area are included in the Ethernet header. The D-IP area and the S-IP area are included in the IP header. The MAC address of the second ECU 4 is stored in the D-MAC area of the IPv4 frame that the L3 switch 12 transfers to the second ECU 4.

[0043] The MAC address of the L3 switch 12 is stored in the S-MAC area of the IPv4 frame that the L3 switch 12 transfers to the second ECU 4. "20" is stored in the VID area of the IPv4 frame that the L3 switch 12 transfers to the second ECU 4.

[0044] In the D-IP area of the IPv4 frame transferred by the L3 switch 12 to the second ECU 4, the IP address of the second ECU 4 is stored. In the S-IP area of the IPv4 frame transferred by the L3 switch 12 to the second ECU 4, the IP address of the first ECU 3 is stored.

[0045] Also, the first ECU 3 and the second ECU 4 are configured to transmit ARP requests and ARP responses. An ARP request is a communication frame that requests the MAC address of a device having a destination IP address. An ARP response is a communication frame that returns a MAC address in response to an ARP request.

[0046] An ARP request and an ARP response are formed by adding a preamble, a destination MAC address, a source MAC address, and a type to an ARP packet. An ARP packet includes an operation area, a source MAC address area, a source IP address area, a target MAC address area, and a target IP address area.

[0047] In the operation area, information indicating whether it is an ARP request or an ARP response is stored. In the source MAC address area, the MAC address of the source is stored. In the source IP address area, the IP address of the source is stored. In the target MAC address area, the MAC address of the destination is stored. In the target IP address area, the IP address of the destination is stored.

[0048] Next, the procedure of the process executed when the L3 switch 12 receives a communication frame will be described. When receiving a communication frame, as shown in FIG. 3, the L3 switch 12 determines at S10 whether the received communication frame satisfies a preset request detection condition.

[0049] The request detection conditions of this embodiment are that all of the following first detection determination condition, second detection determination condition, and third detection determination condition are satisfied. The first detection determination condition is that the communication frame is an ARP request. Specifically, an identification number (for example, 0x0001) indicating that it is an ARP request is stored in the operation area set in the communication frame.

[0050] The second detection determination condition is that the IP address of the L3 switch 12 is stored in the search IP address area set in the communication frame. The third detection determination condition is that the MAC address of a device other than the L3 switch 12 (hereinafter referred to as another device) is stored in the source MAC address area set in the communication frame.

[0051] In S10, when the received communication frame does not satisfy the request detection conditions, the L3 switch 12 relays the received communication frame in S20 and ends the process.

[0052] In S10, when the received communication frame satisfies the request detection conditions, the L3 switch 12 transmits a request detection notification to the SPI communication unit 23 of the MPU11 in S30, for example, according to the SPI protocol, and ends the process. The MAC address stored in the source MAC address area of the received communication frame (that is, the MAC address of another device) is added to the request detection notification. However, the MAC address of another device may or may not be added.

[0053] Next, the procedure of the response transmission process executed by the control unit 21 of the MPU11 will be described. The response transmission process is a process that is repeatedly executed while the MPU11 is running. When the response transmission process is executed, as shown in FIG. 4, the CPU 31 of the control unit 21 determines at S110 whether a request detection notification has been received from the L3 switch 12. Here, if the request detection notification has not been received, the CPU 31 ends the response transmission process.

[0054] On the other hand, if the request detection notification is received, the CPU 31 acquires the fixed message 35 from the RAM 33 at S120. The fixed message 35 is set in the form of an ARP packet. That is, the fixed message 35 includes an operation area, a source MAC address area, a source IP address area, a destination MAC address area, and a destination IP address area.

[0055] An identification number (for example, 0x0002) indicating that it is an ARP response is stored in the operation area of the fixed message 35. The MAC address of the L3 switch 12 is stored in the source MAC address area of the fixed message 35. The IP address of the L3 switch 12 is stored in the source IP address area of the fixed message 35. Note that the addresses of the other devices are usually stored in the destination MAC address area and the destination IP address area of the fixed message 35.

[0056] Next, the CPU 31 generates a communication frame including the fixed message 35 acquired at S120 at S130. Specifically, the CPU 31 generates a communication frame by adding the above preamble, destination MAC address, source MAC address, and type to the fixed message 35 (that is, the ARP packet) acquired at S120. Note that the destination MAC address is the MAC address added to the received request detection notification. However, if no MAC address is added to the request detection notification, a pre-specified value is stored. The source MAC address is the MAC address of the L3 switch 12.

[0057] Then, at S140, the CPU 31 causes the communication frame generated at S130 to be transmitted to the L3 switch 12, and ends the response transmission process. The relay device 2 configured as described above has the first communication line 5 and the second communication line 6 connected thereto, and is configured to relay communication frames between the first ECU 3 and the second ECU 4 connected to the first communication line 5 and the second communication line 6, respectively.

[0058] The relay device 2 includes an L3 switch 12, a control unit 21, and a RAM 33. The L3 switch 12 is configured to execute a relay process for relaying communication frames. The control unit 21 is configured to control the relay device 2.

[0059] The RAM 33 is configured to store a preset fixed message 35. The L3 switch 12 is configured to determine whether or not it has received a communication frame (hereinafter, a specific frame) that satisfies a preset request detection condition from the first ECU 3 and the second ECU 4.

[0060] When the L3 switch 12 determines that it has received a specific frame, the control unit 21 is configured to transmit a communication frame (hereinafter, a fixed frame) including the fixed message 35. In such a relay device 2, even when the L3 switch 12 is configured as hardware, the L3 switch 12 performs a simple process of determining whether or not it has received a specific frame, and the control unit 21 performs a process of transmitting a fixed frame corresponding to the specific frame. Thereby, the relay device 2 can realize a function of appropriately responding to a specific request.

[0061] Furthermore, in the relay device 2, the control unit 21 transmits a fixed frame including the fixed message 35 preset in the RAM 33 as a response corresponding to the specific frame. Thereby, the relay device 2 can realize the process of transmitting the fixed frame with small-scale software.

[0062] As described above, the relay device 2 can implement a function of making an appropriate response to a specific request with small-scale software. Also, the relay device 2 transmits and receives communication frames to and from the first ECU 3 and the second ECU 4 in accordance with the Ethernet protocol. The specific frame is an ARP request. The fixed message is an ARP packet storing the MAC address of the L3 switch 12. Accordingly, the relay device 2 can implement with small-scale software a process of transmitting an ARP response in response to the received ARP request.

[0063] Also, the L3 switch 12 is configured to determine whether or not the received communication frame satisfies preset request detection conditions (that is, by using a packet filter), thereby determining whether or not the specific frame has been received. Accordingly, the relay device 2 can easily detect the reception of the specific frame by utilizing the function of the L3 switch 12.

[0064] Also, the L3 switch 12 is configured to determine whether or not an ARP request has been received for each of the first ECU 3 and the second ECU 4. The control unit 21 is configured to switch the information included in the ARP response by storing, as the destination of the ARP response, the MAC address of the ECU that is the source of the ARP response in accordance with the first ECU 3 and the second ECU 4 that have transmitted the ARP request. Accordingly, the relay device 2 can make an appropriate response to a specific request of each of the first ECU 3 and the second ECU 4.

[0065] In the embodiment described above, the first communication line 5 and the second communication line 6 correspond to a plurality of communication lines, the first ECU 3 and the second ECU 4 correspond to a plurality of communication devices, the L3 switch 12 corresponds to a relay process execution unit, and the RAM 33 corresponds to a message storage unit.

[0066] Also, S10 and S30 correspond to the processing as a specific frame detection unit, and S110 to S140 correspond to the processing as a fixed frame transmission unit. [Second Embodiment] The second embodiment of the present disclosure will be described below with reference to the drawings. In the second embodiment, the parts different from the first embodiment will be described. The same reference numerals are given to the common configurations.

[0067] The communication system 1 of the second embodiment is different from the first embodiment in that the processing executed by the L3 switch 12 and the response transmission processing executed by the MPU 11 are changed. The processing executed by the L3 switch 12 in the second embodiment is different from the first embodiment in that the processing of S35 is executed instead of S30.

[0068] That is, as shown in FIG. 5, in S10, when the received communication frame satisfies the request detection condition, the L3 switch 12 increments (i.e., adds 1) the request detection counter provided in advance in the L3 switch 12 corresponding to the MAC address stored in the transmission source MAC address area of the received communication frame at S35, and ends the processing.

[0069] The L3 switch 12 is provided with a request detection counter corresponding to the first ECU 3 and a request detection counter corresponding to the second ECU 4. Therefore, when the MAC address stored in the transmission source MAC address area of the received communication frame is "MAC-A", the L3 switch 12 increments the request detection counter corresponding to the first ECU 3 at S35.

[0070] Also, when the MAC address stored in the transmission source MAC address area of the received communication frame is "MAC-B", the L3 switch 12 increments the request detection counter corresponding to the second ECU 4 at S35.

[0071] Next, the response transmission process of the second embodiment differs from the first embodiment in that it is executed every time a preset execution cycle elapses, and in that the processes of S210 and S220 are executed instead of S110.

[0072] That is, when the response transmission process of the second embodiment is executed, the CPU 31 of the control unit 21 polls the L3 switch 12 at S210 as shown in FIG. 6, and thereby obtains the value of the request detection counter corresponding to the first ECU 3 and the value of the request detection counter corresponding to the second ECU 4.

[0073] Then, at S220, the CPU 31 determines whether the request detection counter has been incremented for each of the first ECU 3 and the second ECU 4 based on the values of the two request detection counters obtained at S210.

[0074] Here, if the request detection counter has not been incremented for both the first ECU 3 and the second ECU 4, the CPU 31 ends the response transmission process. On the other hand, if the request detection counter has been incremented for at least one of the first ECU 3 and the second ECU 4, the CPU 31 proceeds to S120. That is, when the request detection counter of the first ECU 3 is incremented, the CPU 31 generates and transmits a communication frame to be transmitted to the first ECU 3, and when the request detection counter of the second ECU 4 is incremented, the CPU 31 generates and transmits a communication frame to be transmitted to the second ECU 4.

[0075] In the relay device 2 configured as described above, when the L3 switch 12 determines that it has received a specific frame, the request detection counter provided in the L3 switch 12 is configured to increment. The control unit 21 is configured to obtain the value of the request detection counter by polling the L3 switch 12. Thereby, the control unit 21 can determine whether a specific frame has been received by a simple method of obtaining information from the L3 switch 12. For this reason, the relay device 2 can realize the function of making an appropriate response to a specific request with small-scale software.

[0076] In the embodiment described above, S10 and S35 correspond to the processing as the specific frame detection unit, S210, S220, and S120 to S140 correspond to the processing as the fixed frame transmission unit, and the increment of the request detection counter corresponds to the detection information.

[0077] As described above, one embodiment of the present disclosure has been described. However, the present disclosure is not limited to the above embodiment and can be implemented with various modifications. [Modification Example 1] In the above embodiment, the form in which the first ECU 3 is connected to the first communication line 5 and the second ECU 4 is connected to the second communication line 6 is shown. However, a plurality of ECUs may be connected to the first communication line 5 and the second communication line 6 respectively. [Modification Example 2] In the above second embodiment, the form in which the request detection counter provided in the L3 switch 12 is incremented when a specific frame is received is shown. However, when a specific frame is received, detection information indicating that the specific frame has been received may be stored in the L3 switch 12.

[0078] The control unit 21 and its method described in the present disclosure may be implemented by a dedicated computer configured by a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit 21 and its method described in the present disclosure may be implemented by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Or, the control unit 21 and its method described in the present disclosure may be implemented by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured by one or more hardware logic circuits. Further, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executable by a computer. The method for realizing the functions of each part included in the control unit 21 does not necessarily have to include software, and all of its functions may be realized using one or more hardware.

[0079] A plurality of functions of one component in the above embodiment may be realized by a plurality of components, or one function of one component may be realized by a plurality of components. Also, a plurality of functions of a plurality of components may be realized by one component, or one function realized by a plurality of components may be realized by one component. Further, a part of the configuration of the above embodiment may be omitted. Also, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of another above embodiment.

[0080] In addition to the above-described relay device 2, the present disclosure can also be realized in various forms such as a system including the relay device 2 as a component, a program for causing a computer to function as the relay device 2, a non-transitory physical recording medium such as a semiconductor memory storing this program, and a control method. [Technical idea disclosed in this specification] [Item 1] A relay device (2) configured to connect a plurality of communication lines (5, 6) and relay a communication frame between a plurality of communication devices (3, 4) connected to each of the plurality of communication lines. A relay processing execution unit (12) configured to execute a relay process for relaying the communication frame. A control unit (21) configured to control the relay device. A message storage unit (33) configured to store a preset fixed message (35). The relay processing execution unit Includes a specific frame detection unit (S10, S30, S35) configured to determine whether a specific frame, which is a specific communication frame, has been received from the communication device. The control unit When the specific frame detection unit determines that the specific frame has been received, it includes a fixed frame transmission unit (S110~S140, S210~S220) configured to transmit a fixed frame, which is the communication frame including the fixed message.

[0081] [Item 2] The relay device according to Item 1, wherein The relay device transmits and receives the communication frame to and from the plurality of communication devices according to the Ethernet protocol. The specific frame is an ARP request. The fixed message is an ARP packet storing the MAC address of the relay processing execution unit.

[0082] [Item 3] The relay device according to Item 1 or Item 2, wherein The specific frame detection unit is configured to determine whether the specific frame has been received using a packet filter.

[0083] [Item 4] The relay device according to any one of Items 1 to 3, wherein When the specific frame detection unit determines that it has received the specific frame, it is configured to store detection information indicating that fact in the relay processing execution unit. The control unit is a relay device configured to obtain the detection information by polling the relay processing execution unit.

[0084] [Item 5] The relay device according to any one of Items 1 to 4, The relay processing execution unit is configured to determine whether or not the specific frame has been received for each of the plurality of communication devices. The fixed frame transmission unit is a relay device configured to switch the information included in the fixed frame according to the communication device that has transmitted the specific frame.

[0085] [Item 6] The relay device according to Item 5, The relay device transmits and receives the communication frame to and from the plurality of communication devices according to the Ethernet protocol. The MAC address of the communication device that is the source of the specific frame is stored in the specific frame. The MAC address of the communication device that is the source of the specific frame is stored as the destination of the fixed frame in the fixed frame.

Explanation of Signs

[0086] 2... Relay device, 3... First ECU, 4... Second ECU, 5... First communication line, 6... Second communication line, 12... L3 switch, 21... Control unit, 33... RAM, 35... Fixed message

Claims

1. A relay device (2) connected to a plurality of communication lines (5, 6) and configured to relay communication frames between a plurality of communication devices (3, 4) connected to each of the plurality of communication lines, a relay processing execution unit (12) configured to execute a relay processing for relaying the communication frame; A control unit (21) configured to control the relay device; a message storage unit (33) configured to store a preset fixed message (35); The relay process execution unit, a specific frame detection unit (S10, S30, S35) configured to determine whether or not a specific frame that is a specific communication frame is received from the communication device; The control unit is A relay device comprising a fixed frame transmitting unit (S110 to S140, S210 to S220) configured to transmit a fixed frame, which is the communication frame including the fixed message, when the specific frame detection unit determines that the specific frame has been received.

2. The relay device according to claim 1 , the relay device transmits and receives the communication frames to and from the plurality of communication devices in accordance with an Ethernet protocol; the specific frame is an ARP request, The fixed message is an ARP packet storing the MAC address of the relay process execution unit.

3. 3. The relay device according to claim 1, The relay device is configured so that the specific frame detection unit uses a packet filter to determine whether or not the specific frame has been received.

4. 3. The relay device according to claim 1, the specific frame detection unit is configured to, when determining that the specific frame has been received, store detection information indicating that the specific frame has been received in the relay process execution unit; The relay device configured so that the control unit acquires the detection information by polling the relay process execution unit.

5. The relay device according to claim 1 or 2, the relay process execution unit is configured to determine whether or not the specific frame has been received for each of the plurality of communication devices; The relay device is configured such that the fixed frame transmitting unit switches information included in the fixed frame depending on the communication device that transmitted the specific frame.

6. The relay device according to claim 5 , the relay device transmits and receives the communication frames to and from the plurality of communication devices in accordance with an Ethernet protocol; The specific frame stores a MAC address of the communication device that is a source of the specific frame, A relay device in which the MAC address of the communication device that is the source of the specific frame is stored as the destination of the fixed frame in the fixed frame.

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