Network system

Abstract

To convey the loss of a communication message to an end device, which is a transmission source, even when the loss of the communication message occurs in a relay device to which the end device, which is the transmission source of the communication message, is not directly connected.SOLUTION: Gateway ECUs 10, 20, and 30 monitor whether a communication message has been lost. When a loss of a communication message is detected, each gateway ECU generates a message for loss notification to notify the loss of the communication message, including information for identifying the lost communication message and loss location information indicating at which gateway ECU the communication message was lost, and transmits the message for loss notification to the receiving bus that received the lost notification message. The gateway ECU that received the message for loss notification relays the message for loss notification to the receiving bus that received the lost notification message.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present disclosure relates to a network system in which end devices transmit and receive communication messages to each other via a plurality of relay devices. [Background technology]

[0002] For example, Patent Document 1 describes that in an in-vehicle network, when normal communication via a transmission line becomes impossible, a gateway device (relay device) identifies the state of a transmission line abnormality (transmission line disconnection / transmission line short circuit: recessive fixation / transmission line short circuit: dominant fixation / communication impossible state due to noise) based on the standard error management function defined in CAN communication (error states such as transmission error counter, reception error counter, and bus off) and information on whether a frame can be transmitted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6176199 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, if the transmission of a communication message is delayed at a relay device and the delay time exceeds a predetermined time, the communication message may be discarded. In this case, as described in Patent Document 1, if there is only one relay device in the network, the relay device can easily notify the source node (end device) of the loss of the communication message. Then, based on the notification that the communication message has been lost, the source end device can resend the communication message as necessary.

[0005] However, as networks, such as in-vehicle networks, become larger in scale in recent years, there are also increasing cases where multiple interconnected relay devices are provided within a network. In such cases, if a communication message is lost in a relay device that is not directly connected to the end device that sent the communication message, it becomes difficult to notify the end device that sent the communication message that the communication message has been lost.

[0006] The present disclosure has been made in consideration of the above-mentioned points, and aims to provide a network system that is capable of notifying the end device that is the source of a communication message of its loss, even if the loss of the communication message occurs at a relay device to which the end device that is the source of the communication message is not directly connected. [Means for solving the problem]

[0007] In order to achieve the above object, a network system (100) according to the present disclosure is a network system in which end devices (11, 21, 31) transmit and receive communication messages to each other via a plurality of relay devices (10, 20, 30), Each of the plurality of relay devices a monitoring unit (106) that monitors whether or not a communication message is lost when the communication message is relayed; a generating unit (107) that generates a loss notification message for notifying the loss of the communication message when the monitoring unit detects the loss of the communication message; The plurality of relay devices are configured to transmit or relay the lost notification message to the receiving bus on which the lost notification message was received.

[0008] With the above configuration, each relay device monitors whether or not a communication message has been lost. When loss of a communication message is detected, a loss notification message is generated to notify the loss of the communication message. Each relay device transmits or relays the loss notification message to the receiving bus that received the lost notification message. As a result, the loss notification message is transmitted to the end device that is the source of the communication message. Therefore, even if loss of a communication message occurs in a relay device to which the end device that is the source of the communication message is not directly connected, the end device that is the source of the communication message can confirm the loss of the communication message by receiving the loss notification message.

[0009] The reference numbers in parentheses above merely indicate an example of a correspondence with specific configurations in the embodiments described below, in order to facilitate understanding of the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

[0010] Furthermore, the technical features of the present disclosure other than those described above will become apparent from the following description of the embodiments and the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a configuration diagram showing a configuration of a network system according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the functions of each gateway ECU. [Figure 3] FIG. 10 is a diagram showing an example of a loss notification message. [Figure 4] 10 is a flowchart showing a process executed in each gateway ECU. [Figure 5] 5 is a flowchart showing details of the process of transferring the loss notification message in step S140 of the flowchart in FIG. 4. [Figure 6] 5 is a flowchart showing details of the message loss check and processing in the event of loss in step S150 of the flowchart in FIG. 4. [Figure 7] FIG. 2 is an explanatory diagram for explaining a relay process of a communication message by each gateway ECU. [Figure 8] FIG. 10 is an explanatory diagram for explaining a relay process of a loss notification message by each gateway ECU. [Figure 9] 10 is an explanatory diagram for explaining a process performed by each gateway ECU to generate and transmit a loss notification message when a communication message is lost. FIG. [Figure 10] 10A and 10B are diagrams illustrating a state in which a loss notification message is lost in each gateway ECU. [Figure 11] FIG. 1 is an explanatory diagram for explaining advantages of a network system according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of a network system according to the present disclosure will be described with reference to the drawings. The network system according to the present disclosure can be used, for example, as an in-vehicle network system that enables various terminal ECUs (terminal devices) mounted on a vehicle to communicate with each other. However, application examples of the network system according to the present disclosure are not limited to in-vehicle network systems, and it can also be used as a network system including multiple ECUs for controlling robots, production equipment, buildings, etc.

[0013] Fig. 1 is a configuration diagram showing the configuration of a network system 100 according to this embodiment. As shown in Fig. 1, the network system 100 includes, for example, multiple gateway ECUs 10, 20, and 30 that function as relay devices. Note that Fig. 1 shows an example in which the network system 100 includes three gateway ECUs 10, 20, and 30, but the network system 100 may also be provided with two gateway ECUs, or four or more gateway ECUs.

[0014] The network system 100 can use, for example, CAN (registered trademark, the same applies hereinafter) as a communication protocol. However, the communication protocol is not limited to CAN, and the network system 100 can employ various communication protocols such as CAN-FD, Ethernet (registered trademark), FlexRay (registered trademark), and LIN (Local Interconnect Network). Furthermore, in the network system 100, different types of communication protocols may be employed in the different communication buses 12, 22, 32, 40, and 50. In this case, each of the gateway ECUs 10, 20, and 30 is configured to have a conversion function for converting the protocol of a communication message when transferring a communication message between communication buses having different communication protocols.

[0015] The gateway ECU 10 is connected to a first local bus 12 and a first backbone bus 40 as communication buses. The gateway ECU 20 is connected to a second local bus 22, a first backbone bus 40, and a second backbone bus 50 as communication buses. The gateway ECU 30 is connected to a third local bus 32 and a second backbone bus 50 as communication buses. Each local bus 12, 22, 32 communicatively connects each gateway ECU 10, 20, 30 to a corresponding terminal ECU 11, 21, 31. Each backbone bus 40, 50 communicatively connects the gateway ECUs 10, 20, 30 to each other. Note that while FIG. 1 shows an example in which one local bus 12, 22, 32 is connected to each gateway ECU 10, 20, 30, respectively, the number of local buses connected to each gateway ECU 10, 20, 30 may be two or more.

[0016] An end ECU 11 serving as an end device is connected to the first local bus 12. An end ECU 21 is connected to the second local bus 22. An end ECU 31 is connected to the third local bus 32. Each of the end ECUs 11, 21, and 31 is, for example, an ECU (electronic control unit) for controlling a predetermined control object. Each of the end ECUs 11, 21, and 31 obtains information necessary for controlling the respective control object from or provides information to the other end ECUs, for example, by sending and receiving communication messages. Note that any of the end ECUs may calculate a predetermined physical quantity based on the detection results of a sensor. Furthermore, the number of end ECUs connected to each of the local buses 12, 22, and 32 may be two or more.

[0017] The gateway ECU 10 and the gateway ECU 20 are connected to each other via a backbone bus 40 so that they can communicate with each other. The gateway ECU 20 and the gateway ECU 30 are connected to each other via a backbone bus 50 so that they can communicate with each other.

[0018] Each of the gateway ECUs 10, 20, and 30 has a function of relaying communication messages between the local buses 12, 22, and 32 and the backbone buses 40 and 50 connected thereto. Each of the gateway ECUs 10, 20, and 30 also has a function of monitoring whether or not a communication message being relayed has been lost, and when loss of a communication message is detected, transmitting or relaying a loss notification message to notify the end ECU that is the sender of the communication message that the communication message has been lost.

[0019] The multiple gateway ECUs 10, 20, and 30 each include a computer equipped with a processor, memory, storage, and the like. The processor is, for example, a CPU, MPU, GPU, or DFP that executes predetermined processing according to software. The memory is a volatile storage medium, such as RAM, that temporarily stores the results of the processor's arithmetic processing. The storage includes non-volatile storage media, such as flash memory and ROM. The storage of each of the multiple gateway ECUs 10, 20, and 30 stores a relay processing program for executing processing to relay communication messages executed by the processor. Furthermore, the storage of each of the multiple gateway ECUs 10, 20, and 30 also stores a processing program that monitors whether or not a communication message has been lost and generates a loss notification message when loss is detected. The processing programs executed in the multiple gateway ECUs 10, 20, and 30 will be described in detail later. Note that some or all of the functions provided in the plurality of gateway ECUs 10, 20, and 30 may be realized by hardware using, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0020] The gateway ECUs 10, 20, and 30 may have a diagnostic connector to which a diagnostic device (not shown) is connected. When the diagnostic device is connected to the diagnostic connector, the diagnostic device acquires, for example, diagnostic data recorded when some abnormality occurs from the gateway ECUs 10, 20, and 30 and each of the terminal ECUs 11, 21, and 31. The diagnostic device then diagnoses the presence or absence of an abnormality and, if an abnormality occurs, the type of abnormality based on the acquired diagnostic data. At this time, if there is abnormality information recorded when the number of message losses exceeds a threshold, as described below, each gateway ECU 10, 20, and 30 provides the diagnostic device with information indicating the type of lost message and the number of losses in addition to the abnormality information.

[0021] 2 is a block diagram showing the functions of each of the gateway ECUs 10, 20, and 30. The gateway ECUs 10, 20, and 30 may be configured in the same manner. Therefore, FIG. 2 shows the configuration of the gateway ECU 10 as a representative example. However, each of the gateway ECUs 10, 20, and 30 may have additional configurations or functions added individually as needed.

[0022] As shown in FIG. 2, the gateway ECU 10 includes communication controllers 101 and 102, message transmission / reception units 103 and 104, a message relay unit 105, a message loss monitoring unit 106, a loss notification message generating unit 107, and an ECU abnormality detecting unit .

[0023] The communication controllers 101 and 102 are provided for the respective communication buses 12 and 40 connected to the gateway ECU 10. The communication controllers 101 and 102 are capable of receiving communication signals corresponding to messages sent via the communication buses 12 and 40, and sending communication signals corresponding to messages to the communication buses 12 and 40. In other words, the communication controllers 101 and 102 are capable of sending and receiving various messages via the communication buses 12 and 40.

[0024] The message transmitting / receiving units 103 and 104 are provided for each of the communication controllers 101 and 102. The message transmitting / receiving units 103 and 104 include a receiving buffer and a transmitting buffer (not shown). When a message is received by the communication controller 101 or 102, the message transmitting / receiving unit 103 writes the received message into the receiving buffer. This received message is read by the message relay unit 105 and transferred to another communication bus as necessary. Furthermore, when the message relay unit 105 writes a message into the transmitting buffer, the message transmitting / receiving units 103 and 104 output the written message to the communication controller 101 or 102. When the communication controller 101 or 102 receives a message from the message transmitting / receiving units 103 and 104, it transmits a communication signal corresponding to the message via the communication buses 12 and 40.

[0025] The message relay unit 105 determines the communication bus to which the message is to be forwarded based on the ID of the message received by the message sending / receiving units 103 and 104 and the communication bus 12, 40 that received the message. The message relay unit 105 stores a table that shows the correspondence between the message ID, the communication bus 12, 40 that received the message, and the communication bus 12, 40 that is to be the forwarding destination. By referring to the table, the message relay unit 105 can determine whether the received message needs to be forwarded, and if forwarding is necessary, the communication bus 12, 40 to which the message is to be forwarded.

[0026] Here, when the message relay unit 105 transfers a communication message transmitted from one of the end ECUs 11, 21, 31, the communication message may be lost in the gateway ECUs 10, 20, 30. For example, if there is no free space in the transmission buffer of the message transmitting / receiving unit 104 corresponding to the destination communication bus 12, 40, the message relay unit 105 overwrites the communication message to be transferred with a communication message in one of the transmission buffers, and the overwritten communication message is lost. Alternatively, if the communication load on the communication bus 12, 40 is high and the communication controllers 101, 102 are waiting to transmit a communication message, and the waiting time exceeds a predetermined time, the communication message waiting to be transmitted may be discarded. In this case, the discarded communication message is also lost in the gateway ECUs 10, 20, 30.

[0027] When such a communication message is lost, if the gateway ECU 10, 20, 30 in which the communication message is lost is not directly connected to the end ECU 11, 21, 31 that transmitted the communication message, it becomes difficult to notify the end ECU 11, 21, 31 that transmitted the communication message that the communication message has been lost. If the source end ECU 11, 21, 31 cannot be notified that the communication message has been lost, the source end ECU 11, 21, 31 cannot resend the communication message even if resend is necessary.

[0028] Therefore, in this embodiment, even if the gateway ECU 10, 20, 30 that has lost the communication message is not directly connected to the end ECU 11, 21, 31 that sent the communication message, the gateway ECU 10 is equipped with a message loss monitoring unit 106 and a loss notification message generating unit 107 so that the gateway ECU 10 can notify the end ECU 11, 21, 31 that sent the communication message of the loss of the communication message.

[0029] The message loss monitoring unit 106 monitors whether or not the communication messages and loss notification messages in the gateway ECUs 10, 20, and 30 have been lost. That is, the message loss monitoring unit 106 monitors both communication messages and loss notification messages for loss. When the message loss monitoring unit 106 detects the loss of a communication message, it provides the loss detection result, including information identifying the lost message (e.g., a message ID) and the message type, to the loss notification message generating unit 107. On the other hand, even if the message loss monitoring unit 106 detects the loss of a loss notification message, it does not provide the loss detection result to the loss notification message generating unit 107. Therefore, in this embodiment, even if a loss notification message is lost, no notification of the loss is made. Furthermore, the message loss monitoring unit 106 provides both the loss detection result when it detects the loss of a communication message and the loss detection result when it detects the loss of a loss notification message to the ECU abnormality detection unit 108, which will be described later.

[0030] The loss notification message generating unit 107 generates a loss notification message including information linked to the lost communication message based on the loss detection result that detects that the communication message has been lost. The loss notification message generating unit 107 can generate a loss notification message such as that shown in FIG. 3, for example.

[0031] In the loss notification message shown in Fig. 3, the information associated with the lost communication message can be, for example, information included in the header section that identifies the lost message (e.g., a message ID). Furthermore, the header section also includes a message type that indicates that the message is a loss notification message. However, the information that associates the loss notification message with the lost communication message is not limited to the above-mentioned information, and other information may be used.

[0032] Furthermore, when generating the loss notification message, the loss notification message generator 107 generates loss location information included in the payload portion, which indicates in which of the gateway ECUs 10, 20, and 30 the communication message has been lost. For example, as shown enlarged in FIG. 3, the loss location information associates each data position with the gateway ECU 10, 20, and 30. When loss of a communication message occurs, a set value of "1" is set at the data position corresponding to the gateway ECU 10, 20, and 30 in which loss of the communication message has occurred. FIG. 3 shows loss location information when a communication message has been lost in the gateway ECU 30.

[0033] As a result, when the terminal ECU 11, 21, 31 that is the sender of the lost communication message receives the loss notification message, the sender terminal ECU 11, 21, 31 will be able to understand that the communication message it sent has been lost, information identifying the lost communication message, and information regarding the location at which the communication message was lost, i.e., at which gateway ECU 10, 20, 30.

[0034] The gateway ECUs 10, 20, and 30 further include an ECU abnormality detection unit 108. The ECU abnormality detection unit 108 detects that an abnormality has occurred in the gateway ECUs 10, 20, and 30 based on the loss detection results for the communication messages and the loss notification messages from the message loss monitoring unit 106. For example, the ECU abnormality detection unit 108 can detect that an abnormality has occurred in the gateway ECUs 10, 20, and 30 when it detects, based on the loss detection results from the message loss monitoring unit 106, that the number of message losses has reached a predetermined number or more. When detecting that an abnormality has occurred in the gateway ECUs 10, 20, and 30, the ECU abnormality detection unit 108 records abnormality information indicating that the gateway ECUs 10, 20, and 30 are abnormal. Note that the ECU abnormality detection unit 108 may record the type of lost message and the number of losses each time the message loss monitoring unit 106 detects a message loss.

[0035] Next, the processing executed in the gateway ECUs 10, 20, and 30 will be described in more detail with reference to the flowcharts of Figures 4 to 6. This processing includes a process of relaying communication messages and loss notification messages, and a process of monitoring whether or not a communication message has been lost, and generating a loss notification message when a loss is detected. Note that the processing shown in the flowcharts of Figures 4 to 6 starts when power supply to the gateway ECUs 10, 20, and 30 is turned on, and stops when power supply is turned off.

[0036] In step S100 of the flowchart in FIG. 4, the gateway ECUs 10, 20, and 30 execute initialization processing to initialize various variables, timers, and the like in memories and registers. In step S110, the gateway ECUs 10, 20, and 30 determine whether or not a message has been received from any of the communication buses 12, 22, and 32. Whether or not a message has been received can be determined by whether or not a message has been stored in the receive buffer of the message transmitting / receiving unit 103 or 104. If it is determined that a message has been received, the gateway ECUs 10, 20, and 30 proceed to step S120. If it is determined that a message has not been received, the gateway ECUs 10, 20, and 30 repeatedly execute the processing of step S110 until it determines that a message has been received.

[0037] In step S120, the gateway ECU 10, 20, 30 determines whether the received message is a loss notification message or a communication message. If it is determined to be a communication message, the gateway ECU 10, 20, 30 proceeds to step S130. On the other hand, if it is determined to be a loss notification message, the gateway ECU 10, 20, 30 proceeds to step S140.

[0038] In step S130, the gateway ECU 10, 20, 30 executes a process for transferring the communication message. More specifically, the gateway ECU 10, 20, 30 refers to the table to determine whether or not the transfer of the received message is necessary. If it is determined that the transfer is necessary, the gateway ECU 10, 20, 30 transfers the communication message to the destination communication bus 12, 22, 32, 40, 50, which is determined using the table based on the message ID of the received communication message and the communication bus 12, 40 that received the communication message, as shown in FIG. 7. Thereafter, the gateway ECU 10, 20, 30 executes step S150.

[0039] In step S140, the gateway ECU 10, 20, 30 executes a process for transferring the loss notification message. FIG. 5 is a flowchart illustrating an example of the process for transferring the loss notification message. In step S200 of the flowchart in FIG. 5, the gateway ECU 10, 20, 30 searches for the communication bus 12, 22, 32, 40, 50 to which the loss notification message is to be transferred, based on information identifying the lost communication message contained in the loss notification message. This search can be performed using the table described above. For example, by referring to the table, the gateway ECU 10, 20, 30 can identify the communication bus 12, 22, 32, 40, 50 that received the lost communication message based on the communication bus 12, 22, 32, 40, 50 that received the loss notification message and the information identifying the lost communication message. In this case, the gateway ECU 10, 20, 30 can search for the communication bus 12, 22, 32, 40, 50 that received the lost message as the communication bus 12, 22, 32, 40, 50 to which the loss notification message is to be transferred. In addition, a separate table may be prepared to search for the communication buses 12, 22, 32, 40, and 50 to which the loss notification message is to be transferred, and the gateway ECUs 10, 20, and 30 may use this separately prepared table to search for the communication buses 12, 22, 32, 40, and 50 to which the loss notification message is to be transferred.

[0040] In step S210, the gateway ECU 10, 20, 30 transfers the loss notification message to the communication bus 12, 22, 32, 40, 50 that was searched as the transfer destination, as shown in Fig. 8. Thereafter, the gateway ECU 10, 20, 30 returns to the processing shown in the flowchart of Fig. 4 and executes step S150.

[0041] In step S150, the gateway ECUs 10, 20, and 30 perform a message loss check and processing when a message is lost. FIG. 6 is a flowchart showing an example of the message loss check and processing when a message is lost. In step S300 of the flowchart in FIG. 6, the gateway ECUs 10, 20, and 30 check whether a communication message has been lost and whether a loss notification message has been lost. If a communication message or a loss notification message has been lost, the gateway ECUs 10, 20, and 30 detect information identifying the lost message, the message type, and the like as loss detection results. The processing in step S300 corresponds to the function of the message loss monitoring unit 106.

[0042] In step S310, the gateway ECU 10, 20, 30 determines whether or not a communication message or a loss notification message has been lost based on the loss detection result of step S300. If it is determined that a communication message or a loss notification message has not been lost, the gateway ECU 10, 20, 30 ends the processing shown in the flowchart of Fig. 6. On the other hand, if it is determined that a communication message or a loss notification message has not been lost, the gateway ECU 10, 20, 30 proceeds to step S320.

[0043] In step S320, the gateway ECU 10, 20, 30 determines whether the lost message is a communication message or a loss notification message. If it is determined that the lost message is a communication message, the gateway ECU 10, 20, 30 proceeds to step S330.

[0044] In step S330, the gateway ECU 10, 20, 30 generates loss location information indicating that the communication message has been lost. Then, the gateway ECU 10, 20, 30 creates a loss notification message, as shown in Fig. 3, in which the generated loss location information is set in the payload section and the header section includes information identifying the lost communication message. The processing of steps S310, S320, and S330 corresponds to the function of the loss notification message generation unit 107.

[0045] In step S340, the gateway ECU 10, 20, 30 transmits the created loss notification message to the communication bus 12, 22, 32, 40, 50 that received the lost communication message. In this way, when a communication message is lost during the communication message transfer process, as shown in Fig. 9, the gateway ECU 10, 20, 30 can generate a loss notification message to notify that the communication message has been lost, and transmit the loss notification message toward the end ECU 11, 21, 31 that is the sender of the lost communication message.

[0046] On the other hand, if it is determined in step S320 that the lost message is a loss notification message, the gateway ECUs 10, 20, and 30 skip the processes of steps S330 and S340 and proceed to step S350. Therefore, unlike when a communication message is lost, even if a loss notification message is lost, the gateway ECUs 10, 20, and 30 do not perform the process of generating and transmitting a message to notify of the loss, as shown in FIG.

[0047] In step S350, the gateway ECU 10, 20, 30 determines whether the number of times that communication messages and loss notification messages have been lost is equal to or greater than a predetermined threshold value. If the number of times that messages have been lost is equal to or greater than the predetermined threshold value, the gateway ECU 10, 20, 30 proceeds to step S360. On the other hand, if the number of times that messages have been lost is less than the predetermined threshold value, the gateway ECU 10, 20, 30 ends the process shown in the flowchart of FIG. 6, returns to the process shown in the flowchart of FIG. 4, and executes step S160.

[0048] In step S360, the gateway ECU 10, 20, 30 records abnormality information indicating the occurrence of an abnormality in which messages are lost a predetermined number of times or more. Note that in step S310, the type of lost message and the number of times lost may be recorded each time loss of a communication message or a loss notification message is determined. The processing of steps S350 and S360 corresponds to the function of the ECU abnormality detection unit 108.

[0049] In step S160 of the flowchart in Fig. 4, the gateway ECUs 10, 20, and 30 determine whether the power supply to the gateway ECUs 10, 20, and 30 has been turned off. If the power supply has been turned off, the gateway ECUs 10, 20, and 30 end the processing of the flowchart in Fig. 4. On the other hand, if the power supply has not been turned off, the gateway ECUs 10, 20, and 30 return to the processing of step S110.

[0050] According to the processing shown in the flowcharts of Figures 4 to 6, each gateway ECU 10, 20, 30 monitors whether or not a communication message has been lost. When a loss of a communication message is detected, each gateway ECU 10, 20, 30 generates a loss notification message for notifying the loss of the communication message, including information for identifying the lost communication message and loss location information indicating at which gateway ECU 10, 20, 30 the communication message has been lost, and transmits the loss notification message to the reception bus that received the loss notification message. The gateway ECU 10, 20, 30 that received the loss notification message relays the loss notification message to the reception bus that received the loss notification message. As a result, the loss notification message is transmitted to the end ECU 11, 21, 31 that is the source of the communication message. Therefore, even if a communication message is lost in a gateway ECU 10, 20, 30 to which the end ECU 11, 21, 31 that is the sender of the communication message is not directly connected, the end ECU 11, 21, 31 that is the sender of the communication message can confirm the loss of the communication message by receiving the loss notification message.

[0051] For example, FIG. 11 shows an example in which a communication message Msg1 transmitted from the end ECU 11 is lost in the gateway ECU 30. In this case, the communication message Msg1 transmitted from the end ECU 11 is relayed by the gateway ECUs 10 and 20 and reaches the gateway ECU 30. In response to the loss of the communication message Msg1, the gateway ECU 30 generates a loss notification message Msg2 for notifying the loss of the communication message Msg1 and transmits the loss notification message Msg2 to the communication bus 50 that received the communication message Msg1. Upon receiving the loss notification message Msg2, the gateway ECU 10 and the gateway ECU 20 respectively relay the loss notification message Msg2 to the communication buses 12 and 40 that received the communication message Msg1 linked to the loss notification message Msg2 as the forwarding communication bus. As a result, the end ECU 11 can recognize the loss of the communication message Msg1 that occurred in the gateway ECU 30 and can take action, such as retransmitting the communication message Msg1, if necessary.

[0052] The above describes preferred embodiments of the present disclosure, but the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms within the scope of the gist of the present disclosure. [Explanation of symbols]

[0053] 10: Gateway ECU, 11: End ECU, 12: First local bus, 20: Gateway ECU, 21: End ECU, 22: Second local bus, 30: Gateway ECU, 31: End ECU, 32: Third local bus, 40: First backbone bus, 50: Second backbone bus, 100: Network system, 101: Communication controller, 102: Communication controller, 103: Message sending / receiving unit, 104: Message sending / receiving unit, 105: Message relay unit, 106: Message loss monitoring unit, 107: Loss notification message generating unit, 108: ECU abnormality detection unit

Claims

1. A network system (100) in which terminal devices (11, 21, 31) transmit and receive communication messages to each other via a plurality of relay devices (10, 20, 30), Each of the plurality of relay devices a monitoring unit (106) that monitors whether or not the communication message is lost when relaying the communication message; a generating unit (107) that generates a loss notification message for notifying the loss of the communication message when the monitoring unit detects the loss of the communication message, A network system, wherein the plurality of relay devices transmit or relay the loss notification message to a reception bus that has received the lost notification message.

2. The network system according to claim 1 , wherein the loss notification message includes information associated with the communication message that has been lost.

3. 2. The network system according to claim 1, wherein said loss notification message includes information indicating at which of said plurality of relay devices loss of said communication message occurred.

4. The monitoring unit also monitors whether or not the loss notification message has been lost; 4. The network system according to claim 1, wherein each of the plurality of relay devices further comprises an abnormality detection unit (108) that measures the number of times the communication message and / or the loss notification message is lost, and detects the occurrence of an abnormality when the measured number of times exceeds a predetermined number threshold.

5. 5. The network system according to claim 4, wherein the abnormality detection unit records the type of message that has been lost and the number of times that the message has been lost, in addition to recording the occurrence of the abnormality.

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