Patent Publication Number: US-2022239406-A1

Title: Gateway device, data frame transmission method, and program

Description:
TECHNICAL FIELD 
     The present invention relates to a gateway device, a data frame transmission method, and a program. 
     BACKGROUND ART 
     PTL 1 relates to a communication device, and describes that “the first ECU acquires external information from an external device, and performs information communication based on a communication message defined in a CAN protocol via a communication bus. The first ECU includes: a communication necessity determining unit that determines necessity of information communication via a communication bus on the basis of acquired external information; and a communication control unit that, when the determined necessity of the information communication is “necessary”, stops the information communication for a certain period on condition that a communication error is detected, and restarts the information communication after the certain period has elapsed, and when the determined necessity of the information communication is “unnecessary”, stops transmission of a communication message until a predetermined transmission restart condition is satisfied”. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: JP 5958975 B1 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     The communication device described in PTL 1 stops transmission of a communication message and suppresses power consumption of an electronic control unit (ECU) as a transmission source when determining that a communication error is caused under a specific condition in a case where there is no response from the ECU as a transmission destination of the communication message. However, when the transmission of the communication message is temporarily stopped, the transmission of the communication message is stopped until the recovery of the failed ECU is detected. Therefore, there is a problem that a delay due to a time lag occurs until the transmission of the communication message is resumed after the recovery. 
     In addition, in a case where the condition is not the specific condition, the communication device of the literature continues to retransmit the communication message until the transmission destination ECU recovers, but since the retransmission is periodically repeated at predetermined time intervals, there is a problem that the processing load of the communication device increases. 
     The present invention has been made in view of the above problems, and an object of the present invention is to provide a gateway device capable of suppressing an increase in processing load by adjusting a frame retransmission timing according to a communication status and a load state. 
     Solution to Problem 
     The present application includes a plurality of means for solving at least a part of the above problems, and examples thereof are as follows. A gateway device according to one aspect of the present invention that solves the above problem is a gateway device that relays a data frame between ECUs connected to an in-vehicle network. The gateway device includes: a monitoring processing unit that monitors a predetermined monitored target; and a transmission control unit that transmits the data frame to the ECU. The monitoring processing unit is configured to calculate a transmission interval time of the data frame according to a communication status in the in-vehicle network or a load state of internal processing of the gateway device. The transmission control unit is configured to: transmit the data frame to the ECU based on the calculated transmission interval time. 
     Advantageous Effects of Invention 
     According to the gateway device of the present invention, the increase in the processing load can be suppressed by adjusting the frame retransmission timing according to the communication status and the load state. Other features of the invention will be clear from the description and the accompanying drawings. In addition, objects, configurations, and effects besides the above description will be apparent through the explanation on the following embodiments. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating an example of a schematic configuration of an in-vehicle network system. 
         FIG. 2  is a diagram illustrating an example of a hardware configuration of a gateway device. 
         FIG. 3  is a diagram illustrating an example of a flowchart illustrating a flow of transmission interval adjustment processing. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the invention will be described using the drawings. 
     First Embodiment 
       FIG. 1  is a diagram illustrating an example of a schematic configuration of an in-vehicle network system  1000  according to the present embodiment. The in-vehicle network system  1000  is a network system mounted on a vehicle, and is configured by, for example, a controller area network (CAN). 
     As illustrated, the in-vehicle network system  1000  includes a gateway device  100  and an ECU  200  belonging to individual network connected to the gateway device  100 . The ECUs  200  each transmit and receive a CAN frame (such as data frame and error frame) relayed by the gateway device  100  via a CAN bus, thereby performing information communication with each other. The ECU  200  is a control device used for various controls of the vehicle, and a plurality of ECUs  200  are connected to the gateway device  100  via the CAN bus according to a control target. Examples of the ECU  200  include an engine ECU and a charge control ECU that control a drive system, a steering ECU and a brake ECU that control a traveling system, and a door ECU and a seat ECU that control a vehicle body system. 
     The gateway device  100  includes, for example, a computer, and is a device that relays CAN frames exchanged between various networks included in in-vehicle network system  1000 . Specifically, the gateway device  100  performs relay processing of transmitting a CAN frame acquired from ECU  200  belonging to a certain network to the ECU  200  as a transmission destination. 
     Note that, in a case where the transmission destination ECU  200  fails in function, the gateway device  100  holds the CAN frame that has not been received as a pending frame, and repeats retransmission processing until the CAN frame is received. However, when the processing load of the gateway device  100  increases by repeating the retransmission processing, the frame transmission processing to different ECUs  200  is also affected, and as a result, communication to each network connected to the gateway device  100  is also affected. Therefore, the gateway device  100  monitors whether a predetermined setting condition related to the communication status or the state of the processing load is satisfied, and performs transmission interval adjustment processing of adjusting the transmission timing (transmission time interval) of the pending frame according to the monitoring result. 
     As illustrated in the drawing, the gateway device  100  includes a control unit  10 , a frame buffer  20 , and a CAN controller  30 . Further, the control unit  10  is a functional unit that controls various relay processing of the gateway device  100 , and includes a reception control unit  11 , a transmission control unit  12 , and a monitoring processing unit  13 . 
     The reception control unit  11  is a functional unit that performs reception control of the CAN frame transmitted from the ECU  200  via the CAN controller  30 . 
     The transmission control unit  12  is a functional unit that performs transmission control of a CAN frame to be transmitted to the ECU  200 . Specifically, the transmission control unit  12  transmits the CAN frame to target ECU  200  based on a transmission interval time set in a timer. Further, in a case where a predetermined setting condition is satisfied, the transmission control unit  12  adjusts the transmission interval of the CAN frame. Note that the transmission interval adjustment processing will be described in detail with reference to the flowchart illustrated in  FIG. 3 . 
     The monitoring processing unit  13  is a functional unit that monitors whether a predetermined setting condition related to the communication status or the state of the processing load is satisfied. Specifically, the monitoring processing unit  13  determines whether the quantity of pending frames (the number of pending frames) is equal to or larger than a set threshold (or less than the set threshold). In addition, the monitoring processing unit  13  calculates an interval time (retransmission interval) for changing the transmission interval of the CAN frame to be retransmitted according to the determination result. 
     The frame buffer  20  is a functional unit for temporarily storing a pending frame. Specifically, frame buffer  20  temporarily stores, as a pending frame, a CAN frame that has not been received by a failed ECU  200 . 
     The CAN controller  30  acquires the CAN frame via the CAN bus connected to the gateway device  100 . In addition, the CAN controller  30  transmits the CAN frame related to the relay to the CAN bus. The CAN controller  30  also monitors a communication status of the CAN bus (for example, traffic conditions, load factors, and the like). When the acquired CAN frame is an error frame (error flag), the CAN controller  30  detects a network communication error and counts the number of detected errors. In addition, the CAN controller  30  periodically receives a connection confirmation signal from each ECU  200  via the CAN bus. 
       FIG. 2  is a diagram illustrating an example of a hardware configuration of the gateway device  100 . The gateway device  100  is realized by a high-performance information processing device including an arithmetic device  110 , a main storage device  120 , an external storage device  130 , a communication device  140 , and the CAN controller  30 . 
     The arithmetic device  110  is configured by, for example, a central processing unit (CPU). The main storage device  120  is configured by a memory device such as a random access memory (RAM) or a read only memory (ROM). 
     The external storage device  130  is, for example, a non-volatile storage device such as a hard disk drive, a solid state drive (SSD), or a flash memory. 
     The communication device  140  is, for example, a wireless communication device that performs wireless communication via an antenna. The communication device  140  performs information communication with an external device. 
     The CAN controller  30  is a physical interface that implements a function of the CAN protocol and transmits and receives CAN frames to and from the CAN bus. The CAN controller  30  includes, for example, a microcontroller (microcomputer), a CAN protocol controller, and a CAN transceiver, and there are various types such as a stand-alone type and a microcomputer built-in type. 
     The hardware configuration of the gateway device  100  has been described above. 
     Note that the control unit  10  of the gateway device  100  is realized by a program that causes the arithmetic device  110  to perform processing. This program is stored in the main storage device  120  or the external storage device  130 , loaded on the main storage device  120  when the program is executed, and executed by the arithmetic device  110 . In addition, the frame buffer  20  may be realized by a built-in memory of the CAN controller  30  or the main storage device  120 , or may be realized by a combination thereof. 
     Next, the transmission interval adjustment processing performed by the gateway device  100  will be described. 
       FIG. 3  is a diagram illustrating an example of a flowchart illustrating a flow of the transmission interval adjustment processing. Note that the transmission interval adjustment processing is started when the gateway device  100  is activated. Note that, in the following, an example of a case where the ECU  200  belonging to a certain network fails and the number of pending frames becomes equal to or larger than a threshold and an example of a case where the number of pending frames becomes less than the threshold due to reception of the pending frame by the ECU  200  that has recovered from the failure will be described in order. 
     When the processing is started, the monitoring processing unit  13  monitors a monitored target (Step S 001 ). Specifically, the monitoring processing unit  13  monitors the number of pending frames temporarily stored in the frame buffer  20 . Note that the number of pending frames may be the number of pending frames stored in the frame buffer  20  or the number for each ID (so-called CAN ID) included in the standard format of the CAN frame. 
     Next, the monitoring processing unit  13  determines whether the number of pending frames is equal to or larger than a preset threshold (Step S 002 ). In this example, since it is assumed that the number of pending frames is equal to or larger than the threshold due to a failure of the transmission destination ECU  200  of the CAN frame, the monitoring processing unit  13  determines that the number of pending frames is equal to or larger than the threshold (Yes in Step S 002 ), and calculates a value for extending the transmission interval time (Step S 003 ). Specifically, the monitoring processing unit  13  calculates a time to be added to the currently set transmission interval time for retransmission of the pending frame, and shifts the process to Step S 006 . 
     In Step S 006 , the monitoring processing unit  13  sets, in the timer, the transmission interval time obtained by adding the time calculated in Step S 003  to the currently set transmission interval time for retransmission of the pending frame. 
     Further, the transmission control unit  12  determines whether the set time of the timer has elapsed (Step S 007 ). Then, when it is determined that the set time has not elapsed (No in Step S 007 ), the transmission control unit  12  performs the processing of Step S 007  again. On the other hand, when it is determined that the set time has elapsed (Yes in Step S 007 ), the transmission control unit  12  transmits the pending frame to the target ECU  200  (Step S 008 ; transmission step), the process returns to Step S 001 . 
     When such processing of Steps S 001  to S 008  is repeatedly performed, the transmission interval time of the pending frame set in the timer is gradually extended (the transmission interval is lengthened) in a case where the number of pending frames is accumulated to be equal to or larger than the set threshold. Therefore, the processing load of the gateway device  100 , which is increased by periodically retransmitting the pending frame to the failed ECU  200 , is reduced. 
     In addition, since the gateway device  100  continuously transmits the pending frame while adjusting the transmission interval time, when the ECU  200  recovers from the failure, the pending frame can be delivered to the target ECU  200  without causing a large time lag. 
     As described above, by monitoring the number of pending frames, the gateway device  100  according to the present embodiment adjusts a retransmission timing of the CAN frame according to the communication status in which the CAN frame cannot be transmitted due to the failure of the ECU  200 . As a result, the gateway device  100  can suppress an increase in the processing load. 
     In addition, in the process of Step S 002  executed in a state where the ECU  200  has recovered from the failure and the number of pending frames has become less than the threshold, the monitoring processing unit  13  determines that the number of pending frames is not equal to or larger than the threshold (No in Step S 002 ), and proceeds the process to Step S 004 . 
     In Step S 004 , the monitoring processing unit  13  determines whether the set time of the timer is a normal transmission interval time. Specifically, the monitoring processing unit  13  determines whether the transmission interval time set in the timer is a normal transmission interval time, that is, a transmission interval time to which a time for extending the transmission interval is not added. Then, when it is determined as the normal transmission interval time (Yes in Step S 004 ), the monitoring processing unit  13  shifts the process to Step S 007  and performs the same processing as described above. 
     On the other hand, when the time for extending the transmission interval is added to the timer set time and it is determined that it is not the normal transmission interval time (No in Step S 004 ), the monitoring processing unit  13  calculates a value for shortening the transmission interval time (Step S 005 ). Specifically, the monitoring processing unit  13  calculates a time for decreasing the transmission interval time of the pending frame set when the number of pending frames becomes equal to or larger than the threshold, and shifts the process to Step S 006 . 
     Next, in Step S 006 , the monitoring processing unit  13  sets, in the timer, a transmission interval time obtained by subtracting the time calculated in Step S 005  from the currently set transmission interval time for retransmission of the pending frame, that is, the extended transmission interval time. Then, as described above, after the processing of Step S 007  and Step S 008  is performed, the process returns to Step S 001  again. 
     When such processing of Steps S 001  to S 008  is repeatedly performed, in a case where the number of pending frames is less than the set threshold, the transmission interval time of the pending frame set in the timer is gradually shortened. Therefore, when the ECU  200  recovers from the failure and enters a state in which the pending frame is received, the gateway device  100  can advance the transmission interval time of the pending frame to the target ECU  200  and return the transmission interval time to the normal retransmission time. 
     Note that the transmission interval time set in the timer may be applied only to the transmission timing of the pending frame to the failed ECU  200 , or may be applied to the transmission timing to all the ECUs  200  connected to the gateway device  100 . 
     Second Embodiment 
     In the first embodiment, the transmission interval time for retransmitting the pending frame is adjusted with the number of pending frames as a monitored target. However, in the present embodiment, the transmission interval time is adjusted with the processing load of the gateway device  100  as a monitored target. 
     Specifically, in Step S 001  of the transmission interval adjustment processing, the monitoring processing unit  13  monitors the state of the processing load due to retransmission of the pending frame (monitoring step). More specifically, the monitoring processing unit  13  acquires, from the transmission control unit  12 , information indicating the magnitude of the processing load due to retransmission of the pending frame. 
     Then, the monitoring processing unit  13  adjusts the transmission interval time for retransmission of the pending frame by repeatedly performing the processing in and after Step S 002  described above on the basis of a comparison between the magnitude of the processing load and a threshold of the preset processing load. 
     Similarly to the first embodiment, the transmission interval time set in the timer may be applied only to the transmission timing of the pending frame to the failed ECU  200 , or may be applied to the transmission timing to all the ECUs  200  connected to the gateway device  100 . 
     According to such a gateway device  100 , the retransmission timing of the frame can be adjusted according to the load state increased by the retransmission of the pending frame. Therefore, the gateway device  100  can continue retransmission of the pending frame while suppressing an increase in processing load by periodically retransmitting the pending frame to the failed ECU  200 . 
     Third Embodiment 
     In the second embodiment, the transmission interval time for retransmitting the pending frame is adjusted with the processing load of the gateway device  100  as a monitored target, but the gateway device  100  according to the present embodiment adjusts the transmission interval time with the number of detected communication errors as a monitored target. 
     Specifically, in Step S 001  of the transmission interval adjustment processing, the monitoring processing unit  13  monitors the number of detected communication errors counted by the CAN controller  30  as a monitored target. In addition, the monitoring processing unit  13  determines whether the number of detected errors is equal to or larger than a set threshold (Step S 002 ). 
     When determining that the number of detected communication errors is equal to or larger than the threshold (Yes in Step S 002 ), the monitoring processing unit  13  calculates a value for extending the transmission interval time of the pending frame (Step S 003 ), and adds the calculated time to the current transmission interval time set in the timer (Step S 006 ). Further, the transmission control unit  12  transmits the pending frame to the target ECU  200  according to whether the set time of the timer has elapsed (Steps S 007  and S 008 ). 
     If it is determined in Step S 002  that the number of detected communication errors is not equal to or larger than the threshold (No in Step S 002 ), the monitoring processing unit  13  determines whether the transmission interval time set in the timer is a normal transmission interval time (Step S 004 ). Then, when it is determined that the time for extending the transmission interval is added to the timer set time and is not a normal transmission interval time (No in Step S 004 ), the monitoring processing unit  13  calculates a value for shortening the transmission interval time (Step S 005 ), and sets a transmission interval time obtained by subtracting the calculated time from the currently set transmission interval time for retransmission of the pending frame in the timer (Step S 006 ). 
     Further, the transmission control unit  12  transmits the pending frame to the target ECU  200  according to whether the set time of the timer has elapsed (Steps S 007  and S 008 ). 
     Whether to apply the transmission interval time to only the transmission timing of the pending frame to the target to which the transmission interval time set in the timer is applied, that is, the failed ECU  200 , or whether to apply the transmission interval time to the transmission timing to all the ECUs  200  connected to the gateway device  100  may be determined according to the type of the communication error. For example, when the communication error of which the number of times of detection is equal to or larger than the set threshold is an error frame (error flag) transmitted from the failed ECU  200 , the gateway device  100  may apply the transmission interval time of the pending frame only to the failed ECU  200 . Further, for example, in a case where the communication error of which the number of times of detection is equal to or larger than the set threshold is caused by short circuit (disconnection) of the CAN bus, the gateway device  100  may apply the transmission interval time of the pending frame to all the ECUs  200  connected thereto. 
     According to such a gateway device  100 , it is possible to suppress an increase in the processing load by adjusting the retransmission timing of the frame according to the communication status. In particular, in a status where a communication error occurs, the ECU  200  serving as a transmission target cannot receive a CAN frame in any case of a failure of the ECU  200  or a short circuit of the CAN bus. Therefore, by adjusting the transmission interval of the pending frame to the ECU  200  on the basis of the number of detected communication errors, the gateway device  100  can continuously transmit the pending frame while suppressing an increase in its own processing load. 
     Fourth Embodiment 
     In the third embodiment, the transmission interval time for retransmitting the pending frame is adjusted with the number of detected communication errors as a monitored target, but the gateway device  100  according to the present embodiment adjusts the transmission interval time with the duration of the communication error as a monitored target. 
     Specifically, in Step S 001  of the transmission interval adjustment processing, the monitoring processing unit  13  monitors the duration of the communication error counted by the CAN controller  30  as a monitored target. More specifically, the monitoring processing unit  13  calculates the duration from the occurrence of the communication error for each of a type of the communication error detected by the CAN controller  30  and the transmission destination ECU  200  of the pending frame. For example, when the type of the communication error is a short circuit of the CAN bus, the monitoring processing unit  13  sets a duration from an acquisition time of a frame indicating such a type of communication error to the present as a monitored target. In addition, for example, in a case where the type of the communication error is an error frame transmitted from the failed ECU  200 , the monitoring processing unit  13  sets the duration from the acquisition time of the error frame transmitted from the ECU  200  to the present as a monitored target. 
     In addition, the monitoring processing unit  13  determines whether the duration is equal to or longer than the set threshold (Step S 002 ). When determining that the duration of the communication error is equal to or longer than the threshold (Yes in Step S 002 ), the monitoring processing unit  13  calculates a value for extending the transmission interval time of the pending frame in the same manner as described above (Step S 003 ), and adds the calculated time to the current transmission interval time set in the timer (Step S 006 ). Further, the transmission control unit  12  transmits the pending frame to the target ECU  200  according to whether the set time of the timer has elapsed (Steps S 007  and S 008 ). 
     On the other hand, when it is determined in Step S 002  that the duration of the communication error is not equal to or longer than the threshold (No in Step S 002 ), the monitoring processing unit  13  determines whether the transmission interval time set in the timer is a normal transmission interval time (Step S 004 ), and performs the following processing of Steps S 005  and S 006 . Similarly, the transmission control unit  12  performs the processing of Steps S 007  and S 008 . 
     Whether to apply the transmission interval time to only the transmission timing of the pending frame to the target to which the transmission interval time set in the timer is applied, that is, the failed ECU  200 , or whether to apply the transmission interval time to the transmission timing to all the ECUs  200  connected to the gateway device  100  may be determined according to the type of the communication error as in the third embodiment. 
     According to such a gateway device  100 , it is possible to suppress an increase in the processing load by adjusting the retransmission timing of the frame according to the communication status. In particular, in a status where a communication error occurs, the ECU  200  serving as a transmission target cannot receive a CAN frame in any case of a failure of the ECU  200  or a short circuit of the CAN bus. Therefore, by adjusting the transmission interval of the pending frame to the ECU  200  on the basis of the duration of the communication error, the gateway device  100  can continuously transmit the pending frame while suppressing an increase in its own processing load. 
     Fifth Embodiment 
     In the fourth embodiment, the transmission interval time for retransmitting the pending frame is adjusted with the duration of the communication error as a monitored target. However, the gateway device  100  according to the present embodiment adjusts the transmission interval time with the reception status of the connection confirmation signal periodically transmitted by the ECU  200  as a monitored target. 
     The ECU  200  connected to the CAN bus periodically transmits a connection confirmation signal to a monitoring ECU (not illustrated) for monitoring the state of each ECU  200 . On the other hand, the failed ECU  200  cannot transmit the connection confirmation signal. Therefore, the monitoring processing unit  13  according to the present embodiment monitors the reception status of the connection confirmation signal via the CAN controller  30  to estimate whether the ECU  200  has failed, and adjusts the transmission interval time for retransmission of the pending frame. 
     Specifically, in Step S 001  of the transmission interval adjustment processing, the monitoring processing unit  13  monitors the reception status of the connection confirmation signal as a monitored target. More specifically, the monitoring processing unit  13  monitors whether the connection confirmation signal is periodically transmitted from all ECUs  200  belonging to each network included in the gateway device  100  via the CAN controller  30 . In addition, in a case where there is the ECU  200  from which the reception of the connection confirmation signal is interrupted, the monitoring processing unit  13  counts an interruption duration from the previous reception. 
     In addition, the monitoring processing unit  13  determines whether the interruption duration is equal to or longer than a set threshold (Step S 002 ). Then, when it is determined that the interruption duration is equal to or longer than the threshold (Yes in Step S 002 ), the monitoring processing unit  13  calculates a value for extending the transmission interval time of the pending frame in the same manner as described above (Step S 003 ), and adds the calculated time to the current transmission interval time set in the timer (Step S 006 ). Further, the transmission control unit  12  transmits the pending frame to the target ECU  200  according to whether the set time of the timer has elapsed (Steps S 007  and S 008 ). 
     On the other hand, when it is determined in Step S 002  that the interruption duration is not equal to or longer than the threshold (No in Step S 002 ), the monitoring processing unit  13  determines whether the transmission interval time set in the timer is a normal transmission interval time (Step S 004 ), and performs the following processing of Steps S 005  and S 006 . Similarly, the transmission control unit  12  performs the processing of Steps S 007  and S 008 . 
     Note that the transmission interval time set in the timer may be applied only to the transmission timing of the pending frame to the failed ECU  200 , or may be applied to the transmission timing to all the ECUs  200  connected to the gateway device  100 . 
     According to such a gateway device  100 , it is possible to suppress an increase in the processing load by adjusting the retransmission timing of the frame according to the communication status. In particular, since the ECU  200  in which the periodic transmission of the connection confirmation signal is interrupted is estimated to have a high possibility of failure, the ECU  200  cannot receive the CAN frame. Therefore, by adjusting the transmission interval of the pending frame to the ECU  200  according to the interruption duration of the connection confirmation signal, the gateway device  100  can continuously transmit the pending frame while suppressing an increase in its own processing load. 
     Sixth Embodiment 
     In the first to fifth embodiments described above, the transmission interval time for retransmission of the pending frame is adjusted according to whether a predetermined monitored target is equal to or larger than a set threshold. However, the present invention is not limited to this. For example, when shortening the transmission interval time for retransmission, the gateway device  100  according to the present embodiment calculates the transmission interval time to be shortened in consideration of the communication status, that is, the network traffic load factor. 
     Specifically, in Step S 005  of calculating a value for shortening the transmission interval time of the pending frame, the monitoring processing unit  13  acquires the load factor of the traffic of each network via the CAN controller  30 . Then, for example, the monitoring processing unit  13  calculates a value for shortening the transmission interval time by using predetermined weight values respectively corresponding to a case where the load factor of the traffic is equal to or larger than a predetermined threshold and a case where the load factor of the traffic is less than the predetermined threshold. 
     Note that, in a case where the load factor of the traffic is equal to or larger than a predetermined threshold, the monitoring processing unit  13  associates a weight value with which the calculated value (value for shortening the transmission interval) becomes small. On the other hand, when the load factor of the traffic is less than the predetermined threshold, the monitoring processing unit  13  associates a weight value with which the calculated value (value for shortening the transmission interval) becomes large. 
     The calculation of the transmission interval time by weighting in consideration of such a traffic load factor prevents the network traffic from being instantly congested. For example, when the transmission interval time for retransmission of the pending frame is shortened, it is preferable to transmit all the pending frames to the target ECU  200  at an early interval time. However, when many pending frames are sent to the CAN bus in a short period of time without considering the traffic load factor of the network, the traffic load factor of the network increases at once. In order to prevent this, the gateway device  100  according to the present embodiment calculates a value for shortening the transmission interval time for retransmission of the pending frame in consideration of the traffic load factor. 
     Note that the processing in Steps S 006  to S 008  is similar to that described above, and thus detailed description thereof will be omitted. 
     According to the gateway device  100  as described above, when the transmission interval time for retransmission of the pending frame is shortened, it is possible to suppress an increase in the processing load by adjusting the retransmission timing of the frame according to the communication status and the load state while preventing the traffic of the network from being instantaneously congested. 
     In the first to fifth embodiments described above, when it is determined that the monitored target is less than the predetermined set threshold, the transmission interval time for retransmission of the pending frame is gradually reduced, but the present invention is not limited thereto. For example, when it is determined in Step S 004  described above that the timer set time is not the normal transmission interval time of the pending frame (No in Step S 004 ), that is, when the transmission interval time is set longer than usual, a value to be returned to the normal transmission interval time instead of stepwise may be calculated and set in the timer in Step S 005 . In this way, all the pending frames can be transmitted to the ECU  200  estimated to have recovered from the failure more quickly. 
     Further, such setting of the transmission interval time is effective when combined with the above-described sixth embodiment in which the final transmission interval time is calculated in consideration of the traffic load factor. According to such a combination, since the traffic load factor of the network is taken into consideration, all the pending frames can be transmitted to the target ECU  200  more quickly without tightening the traffic. 
     Further, the invention is not limited to the embodiments described above, but includes various modifications. For example, the above embodiments have been described in detail for easy understanding of the invention, and the invention is not necessarily limited to having all the configurations described. In addition, some of the configurations of a certain embodiment may be replaced with the configurations of the other embodiments, and the configurations of the other embodiments may be added to the configurations of the subject embodiment. It is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. 
     In addition, in the above description, only control lines and information lines considered to be necessary for explanation are illustrated, but not all the control lines and the information lines for a product are illustrated. In practice, almost all the configurations may be considered to be connected to each other. 
     REFERENCE SIGNS LIST 
     
         
           1000  in-vehicle network system 
           100  gateway device 
           10  control unit 
           11  reception control unit 
           12  transmission control unit 
           13  monitoring processing unit 
           20  frame buffer 
           30  CAN controller 
           110  arithmetic device 
           120  main storage device 
           130  external storage device 
           140  communication device 
           150  bus 
           200  ECU