Patent Publication Number: US-2020293218-A1

Title: Vehicle communication system

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2019-048614 filed in Japan on Mar. 15, 2019. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a vehicle communication system. 
     2. Description of the Related Art 
     Examples of a conventional vehicle communication system include a communication system that includes a switching hub for connecting between a plurality of on-vehicle devices and performs communications between the on-vehicle devices via the switching hub. The switching hub has a memory, and the memory has setting information stored therein that is used for setting the operation of the switching hub. Japanese Patent Application Laid-open No. 2016-212044 discloses a communication apparatus that prevents transmission of incorrect messages by limiting write and read into a register. 
     The communication system as described above operates, for example, with the setting information read by the switching hub from the memory. At times, however, the switching hub fails to read the setting information from the memory and consequently fails to operate normally, which may degrade the reliability of the communication system. 
     SUMMARY OF THE INVENTION 
     Given this inconvenience, the present invention has been made to provide a vehicle communication system the reliability of which can be prevented from degrading. 
     In order to achieve the above mentioned object, a vehicle communication system according to one aspect of the present invention includes a plurality of transfer units each including a transfer section installed in a vehicle, connected to a device, and configured to transfer information to the device, and a storage section connected to the transfer section and capable of storing information therein, the transfer section being installed in a vehicle, connected to a device, and configured to transfer information to the device, the storage section being connected to the transfer section and capable of storing information therein, wherein the transfer units are connected to one another, each of the transfer units stores, in the storage section of that transfer unit, setting information applicable for setting operation of the transfer sections in that transfer unit and at least one of the other transfer units, and that transfer unit operates based on the setting information applicable to that transfer unit that has been acquired from the storage section in the other transfer units when failing to acquire the applicable setting information stored in the storage section in that transfer unit. 
     According to another aspect of the present invention, in the vehicle communication system, it is preferable that the vehicle is segmented into a plurality of regions, the regions include a unit region that is a region including two or more of the transfer units, and each of the transfer units included in the unit region stores therein the setting information applicable to that transfer unit and the other transfer unit or units in the unit region and does not store therein any of the setting information applicable to the other transfer units in the other regions. 
     According to still another aspect of the present invention, in the vehicle communication system, it is preferable that when the transfer units include a plurality of acquirement-disabled transfer units that are not enabled to acquire the setting information applicable to and stored in the storage sections in these acquirement-disabled transfer sections units and include at least one acquirement-enabled transfer unit that is enabled to acquire the setting information applicable to and stored in that acquirement-enabled transfer unit, each of the plurality of acquirement-disabled transfer units operates based on the setting information applicable to that acquirement-disabled transfer unit and acquired from the storage section in the same one of the at least one acquirement-enabled transfer unit. 
     The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an example of the configuration of a vehicle communication system according to a first embodiment; 
         FIG. 2  is a block diagram illustrating an example of the operation of the vehicle communication system according to the first embodiment; 
         FIG. 3  is a flowchart illustrating an example of the operation of the vehicle communication system according to the first embodiment; 
         FIG. 4  is a block diagram illustrating an example of the operation of a vehicle communication system according to a second embodiment; and 
         FIG. 5  is a block diagram illustrating an example of the configuration of a vehicle communication system according to a modification of a third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings, the following details modes (embodiments) for carrying out the present invention. Descriptions in the following embodiments are not intended to limit the present invention. The constituent elements described below include those that can be easily conceived by the skilled person and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Various omissions, substitutions, and changes can be made to the configurations without departing from the scope of the present invention. 
     First Embodiment 
     A vehicle communication system  100  according to an embodiment is described with reference to the drawings.  FIG. 1  is a block diagram illustrating an example of the configuration of the vehicle communication system  100  according to the embodiment.  FIG. 2  is a block diagram illustrating an example of the operation of the vehicle communication system  100  according to the embodiment. The vehicle communication system  100  is a system installed in a vehicle and configured to connect a plurality of devices  2  and  3  in the vehicle so that the devices  2  and  3  can communicate with each other. The vehicle communication system  100  includes a plurality of switching hubs  1  as a plurality of transfer units. The respective switching hubs  1  have pluralities of devices  2  and  3  and transfer information to the pluralities of devices  2  and  3 . Each of the switching hubs  1  constitutes an on-vehicle local area network (LAN), which is a communication network provided in the vehicle. For example, the communication standard for Ethernet (registered trademark) is applied to the on-vehicle LAN. This example, however, is not limiting. 
     Each of the switching hubs  1  includes an input-output interface  10 , an external memory  20 , and a switch integrated circuit (IC)  30  as a transfer section. In the first embodiment, the switching hubs  1  include a first switching hub  1 A and a second switching hub  1 B. The first switching hub  1 A includes a first input-output interface  10 A, a first external memory  20 A, and a first switch IC  30 A as illustrated  FIG. 1 . 
     The first input-output interface  10 A is an interface to be connected to various devices. The first input-output interface  10 A is connected to the first switch IC  30 A and is connected via communication lines to the devices  2 . The first input-output interface  10 A includes ports  11   a  to  11   d.  The ports  11   a,    11   b,  and  11   c  are connected to devices  2   a,    2   b,  and  2   c,  respectively, via communication lines. The port lid is connected to the second switching hub  1 B via a communication line. 
     The first external memory  20 A stores information therein. The first external memory  20 A is, for example, a non-volatile memory and is made of a magnetic storage apparatus, an optical disc, or a flash memory. The first external memory  20 A is provided outside the first switch IC  30 A and is connected via a communication line to the first switch IC  30 A. The first external memory  20 A has information stored therein that is needed for putting the switch ICs  30  corresponding to the first external memory  20 A and the other external memory or memories into operation. The first external memory  20 A has setting information stored therein that is used for, for example, setting operation of the first and a second switch ICs  30 A and  30 B. The first external memory  20 A may have, for example, setting information for all of the switches IC  30  included in the vehicle communication system  100 . The setting information applicable to the first switch IC  30 A contains, for example, a routing table. In this routing table, the respective MAC addresses of the devices  2  are associated with port numbers assigned in the first input-output interface  10 A. For example, the MAC address of the device  2   a  is associated with the port number of the port  11   a,  the MAC address of the device  2   b  with the port number of the port lib, the MAC address of the device  2   c  with the port number of the port  11   c,  and the MAC address of the second switching hub  1 B with the port number of the port  11   d.    
     The first switch IC  30 A is connected to the devices  2  to execute a process to transfer information to each of the devices  2 . The first switch IC  30 A is an electronic part obtained by forming elements such as a transistor, a resistance, and a capacitor on a circuit board. The first switch IC  30 A includes a first embedded central processing unit (CPU)  31 A. The first embedded CPU  31 A is mounted on the circuit board for the first switch IC  30 A and embedded in the first switch IC  30 A. The first embedded CPU  31 A is connected to the first external memory  20 A and is connected via the first input-output interface  10 A to the devices  2  and the second switching hub  1 B. 
     The first embedded CPU  31 A operates after reading setting information applicable to the first embedded CPU  31 A from the first external memory  20 A. For example, when the first switching hub  1 A is powered on and started up, the first embedded CPU  31 A reads the setting information applicable thereto from the first external memory  20 A. The first embedded CPU  31 A writes the read setting information applicable thereto into an internal memory (not illustrated) in the first switch IC  30 A and operates based on the setting information thus written into the internal memory. 
     After the startup, the first embedded CPU  31 A transmits information to each of the devices  2  based on the routing table contained in the setting information applicable to the first embedded CPU  31 A. The first embedded CPU  31 A refers to the routing table, for example, when an Ethernet frame is output from the second switching hub  1 B. The first embedded CPU  31 A then compares a destination MAC address contained in the Ethernet frame with the respective MAC addresses of the devices  2  that have been registered in the routing table. The first embedded CPU  31 A then detects the MAC address of the device  2  that is identical to the destination MAC address, and acquires the port number associated with the detected MAC address of the device  2 . The first embedded CPU  31 A then outputs the Ethernet frame to one of the ports  11   a  to  11   c  that is indicated by the acquired port number. 
     The second switching hub  1 B is configured in the same manner as the first switching hub  1 A described above. Specifically, the second switching hub  1 B includes a second input-output interface  10 B, a second external memory  20 B, and a second switch IC  30 B as a transfer section. 
     The second input-output interface  10 B is an interface to be connected to various devices. The second input-output interface  10 B is connected to the second switch IC  30 B and is connected via communication lines to the devices  3 . The second input-output interface  10 B is configured by including ports  12   a  to  12   d.  The ports  12   a,    12   b,  and  12   c  are connected to devices  3   a,    3   b,  and  3   c,  respectively, via communication. The port  12   d  is connected to the first switching hub  1 A via a communication line. 
     The second external memory  20 B stores information therein. The second external memory  20 B is, for example, a non-volatile memory and is made of a magnetic storage apparatus, an optical disc, or a flash memory. The second external memory  20 B is provided outside the second switch IC  30 B and is connected to the second switch IC  30 B via a communication line. The second external memory  20 B has information stored therein that is needed for putting the switch ICs  30  corresponding to the second external memory  20 B and the other external memory or memories into operation. The second external memory  20 B has setting information stored therein that is used for, for example, setting operation of the first and the second switch ICs  30 A and  30 B. The second external memory  20 B may have, for example, setting information applicable to all of the switches IC  30  included in the vehicle communication system  100 . The setting information applicable to the second switch IC  30 B contains, for example, a routing table. In this routing table, the respective MAC addresses of the devices  3  are associated with port numbers assigned in the second input-output interface  10 B. For example, the MAC address of the device  3   a  is associated with the port number of the port  12   a,  the MAC address of the device  3   b  with the port number of the port  12   b,  the MAC address of the device  3   c  with the port number of the port  12   c,  and the MAC address of the first switching hub  1 A with the port number of the port  12   d.    
     The second switch IC  30 B is connected to a plurality of devices  3  to execute a process to transfer information to each of the devices  3 . The second switch IC  30 B is an electronic part obtained by forming elements such as a transistor, a resistance, and a capacitor on a circuit board. The second switch IC  30 B includes a second embedded CPU  31 B. The second embedded CPU  31 B is mounted on the circuit board for the second switch IC  30 B and embedded in the second switch IC  30 B. The second embedded CPU  31 B is connected to the second external memory  20 B and is connected via the second input-output interface  10 B to the devices  3  and the first switching hub  1 A. 
     The second embedded CPU  31 B operates after reading setting information applicable to the second embedded CPU  31 B from the second external memory  20 B. For example, when the second switching hub  1 B is powered on and started up, the second embedded CPU  31 B reads the setting information applicable thereto from the second external memory  20 B. The second embedded CPU  31 B writes the read setting information applicable thereto into an internal memory (not illustrated) in the second switch IC  30 B and operates based on the setting information thus written into the internal memory. 
     After the startup, the second embedded CPU  31 B transmits information to each of the devices  3  based on the routing table contained in the setting information applicable to the second embedded CPU  31 B. The second embedded CPU  31 B refers to the routing table, for example, when an Ethernet frame is output from the first switching hub  1 A. The second embedded CPU  31 B then compares a destination MAC address contained in the Ethernet frame with the respective MAC addresses of the devices  3  that have been registered in the routing table. The second embedded CPU  31 B then detects the MAC address of the device  3  that is identical to the destination MAC address, and acquires the port number associated with the detected MAC address of the device  3 . The second embedded CPU  31 B then outputs the Ethernet frame to one of the ports  12   a  to  12   c  that is indicated by the acquired port number. 
     Described next is a case when the first embedded CPU  31 A fails to read the setting information applicable to the first embedded CPU  31 A from the first external memory  20 A. When failing to read the setting information applicable thereto from the first external memory  20 A, the first embedded CPU  31 A operates based on setting information applicable thereto acquired from another switching hub  1 , for example, the second external memory  20 B in the second switching hub  1 B. The following details a case when failure to read the setting information applicable to the first embedded CPU  31 A occurs. 
     The first embedded CPU  31 A reads the setting information applicable to the first embedded CPU  31 A from the first external memory  20 A when the first switching hub  1 A is started up. However, the first embedded CPU  31 A fails to read the setting information applicable thereto from the first external memory  20 A, for example, when the first external memory  20 A is out of order. Upon occurrence of such a read error, the first embedded CPU  31 A transmits, to the second switching hub  1 B, a request frame F 1  indicating a request for transmission of the setting information of the first embedded CPU  31 A, as illustrated  FIG. 2 . Upon receiving the request frame F 1  from the first switching hub  1 A, the second embedded CPU  31 B of the second switching hub  1 B reads the setting information applicable to the first switch IC  30 A and stored in the second external memory  20 B. The second embedded CPU  31 B then transmits, to the first switching hub  1 A, a response frame F 2  containing the read setting information applicable to the first switch IC  30 A. The first embedded CPU  31 A in the first switching hub  1 A operates based on the setting information applicable thereto contained in the response frame F 2  transmitted from the second switching hub  1 B. 
     Next described is an example of the operation of the vehicle communication system  100  according to the embodiment.  FIG. 3  is a flowchart illustrating an example of the operation of the vehicle communication system  100  according to the embodiment. The first switch IC  30 A (the first embedded CPU  31 A) reads setting information from the first external memory  20 A (step S 1 ). If the first switch IC  30 A has failed to read the setting information from the first external memory  20 A (Yes at step S 2 ), the first switch IC  30 A notifies a passenger of a read error using a warning lamp or the like not illustrated (step S 3 ). 
     Subsequently, the first switch IC  30 A requests an n-th switch IC  30  to transmit setting information (step S 4 ). The n-th switch IC  30  is the n-th switch IC  30 . In this example, the first switch IC  30 A transmits, to the second switch IC  30 B, the request frame F 1  indicating a request for transmission of the setting information. Subsequently, the n-th switch IC  30  receives the transmission request from the first switch IC  30 A (step S 5 ). In this example, the second switch IC  30 B receives the request frame F 1  transmitted from the first switch IC  30 A. 
     Subsequently, the n-th switch IC  30  reads setting information from an n-th external memory  20  (step S 6 ). In this example, the second switch IC  30 B reads the setting information applicable to the first switch IC  30 A and stored in the second external memory  20 B. Subsequently, the n-th switch IC  30  transmits the setting information to the first switch IC  30 A (step S 7 ). In this example, the second switch IC  30 B transmits, to the first switch IC  30 A, the response frame F 2  containing the read setting information applicable to the first switch IC  30 A. Subsequently, the first switch IC  30 A receives the setting information from the n-th switch IC  30  (step S 8 ). In this example, the first switch IC  30 A receives the response frame F 2  containing the setting information applicable to the first switch IC  30 A from the second switch IC  30 B. Subsequently, the first switch IC  30 A reads the setting information contained in a response frame F 2  received thereby (step S 9 ). When the first switch IC  30 A fails to read the setting information applicable thereto contained in the response frame F 2  (Yes at step S 10 ), the first switch IC  30 A determines whether all of the other switches IC  30  have been requested to transmit the setting information (step S 11 ). 
     If any of the other switches IC  30  has not been requested to transmit the setting information (No at step S 11 ), the first switch IC  30 A requests the (n+1)-th switch IC  30  (for example, a third switch IC  30 ) that is the subsequent switch IC  30  to transmit the setting information (steps S 12  and S 4 ). If all of the other switches IC  30  have been requested to transmit the setting information (Yes at step S 11 ), the first switch IC  30 A switches to another communication route (step S 13 ) and stops the first switching hub  1 A from functioning (step S 14 ). The first switch IC  30 A then notifies the passenger using a warning lamp or the like that the first switching hub  1 A has been stopped from functioning (step S 15 ) and ends the process of reading the setting information. 
     If the first switch IC  30 A has not failed to read the setting information from the first external memory  20 A in step S 2  described above (No at step S 2 ), the process of reading the setting information is ended. Additionally, if the first switch IC  30 A has not failed to read the setting information contained in the response frame F 2  (No at step S 10 ), the process of reading the setting information is ended. 
     As described above, the vehicle communication system  100  according to the embodiment includes the switching hubs  1 . The vehicle communication system  100  includes, for example, the first switching hub  1 A and the second switching hub  1 B. The first switching hub  1 A includes: the first switch IC  30 A installed in the vehicle, connected to the devices  2 , and configured to transfer information to each of the devices  2 ; and the first external memory  20 A connected to the first switch IC  30 A and capable of storing information therein. The second switching hub  1 B includes: the second switch IC  30 B installed in the vehicle, connected to the devices  3 , and configured to transfer information to each of the devices  3 ; and the second external memory  20 B connected to the second switch IC  30 B and capable of storing information therein. The first and the second switching hubs  1 A and  1 B are connected to each other and have setting information stored in each of the first and the second external memories  20 A and  20 B. The setting information is applicable for setting the operation of the first and the second switch ICs  30 A and  30 B. When the first switching hub  1 A fails to read the setting information applicable thereto and stored in the first external memory  20 A in the first switching hub  1 A, the first switching hub  1 A operates based on the setting information applicable thereto acquired from the second external memory  20 B. 
     In the vehicle communication system  100 , this configuration enables the first switching hub  1 A to operate based on the setting information applicable thereto acquired from the second external memory  20 B even in a case when the first switching hub  1 A fails to acquire the setting information applicable thereto stored in the first external memory  20 A therein. In the vehicle communication system  100 , this configuration enables the first switching hub  1 A to operate based on the setting information applicable thereto acquired from the second external memory  20 B even in a case when the second switching hub  1 B fails to acquire the setting information applicable thereto stored in the first external memory  20 A therein. Consequently, the vehicle communication system  100  is provided with a fail-safe that enables normal operation even when the external memory  20  is out of order, thereby being improved in reliability. In the vehicle communication system  100 , the fail-safe described above can be implemented by use of electronic parts conventionally used, whereby increase in the number of parts is suppressed. As a result, the vehicle communication system  100  can be light-weight. 
     Second Embodiment 
     Next, a vehicle communication system  100 A according to a second embodiment is described. In the second embodiment, the same reference signs are used to indicate the same constituent elements as those in the first embodiment, and detailed description thereof is omitted. The vehicle communication system  100 A is different from the vehicle communication system  100  according to the first embodiment in that, when errors in reading setting information occur in a plurality of certain memories, the setting information is acquired from the same one of the other external memories  20  upon occurrence of each error. 
     The vehicle communication system  100 A includes the first switching hub  1 A, the second switching hub  1 B, a third switching hub  1 C as illustrated  FIG. 4 . The second embodiment assumes that errors in reading setting information occur in the first switching hub  1 A and the third switching hub  1 C. 
     When an error in reading setting information applicable to the first switching hub  1 A occurs therein, the first switching hub  1 A transmits, to the second switching hub  1 B, a request frame F 1  indicating a request to transmit the setting information applicable thereto. Upon receiving the request frame F 1  from the first switching hub  1 A, the second switching hub  1 B reads the setting information applicable to the first switch IC  30 A and stored in the second external memory  20 B. The second switching hub  1 B then transmits, to the first switching hub  1 A, a response frame F 2  containing the read setting information applicable to the first switch IC  30 A. The first switching hub  1 A operates based on the setting information applicable thereto contained in the response frame F 2  transmitted from the second switching hub  1 B. 
     When an error in reading setting information applicable to the third switching hub  1 C occurs therein, the third switching hub  1 C transmits, to the second switching hub  1 B, a request frame F 1  indicating a request to transmit the applicable setting information. Upon receiving the request frame F 1  from the third switching hub  1 C, the second switching hub  1 B reads the setting information applicable to a third switch IC  30 C and stored in the second external memory  20 B. The second switching hub  1 B then transmits, to the third switching hub  1 C, a response frame F 2  containing the read setting information applicable to the third switch IC  30 C. The third switching hub  1 C operates based on the setting information applicable thereto contained in the response frame F 2  transmitted from the second switching hub  1 B. 
     Thus, in the vehicle communication system  100 A, the switching hubs  1  include two or more acquirement-disabled switching hubs  1  that cannot acquire setting information applicable thereto and stored in the external memories  20  therein, and includes at least one acquirement-enabled transfer unit that can acquire setting information applicable thereto and stored in the external memory  20  therein. In this case, in the switching hubs  1 , the two or more acquirement-disabled switching hubs  1  operate based on the setting information applicable thereto acquired from the external memory  20  in the same acquirement-enabled switching hub  1 . In the vehicle communication system  100 A, this configuration enables a load imposed on the entire system to be distributed, for example, by causing one of the switching hubs  1  that has a relatively small transfer processing load imposed thereon to transmit setting information to the other switching hubs  1 . In the vehicle communication system  100 A, the switching hub  1  that has a relatively small transfer processing load imposed thereon may be previously identified. Alternatively, the switching hub  1  that has a relatively small transfer processing load imposed thereon may be determined based on the result of detection of respective transfer processing loads imposed on the switching hubs  1 . 
     Third Embodiment 
     Next, a vehicle communication system  100 B according to a third embodiment is described. In the third embodiment, the same reference signs are used to indicate the same constituent elements as those in the first embodiment, and detailed description thereof is omitted. The vehicle communication system  100 B is different from the vehicle communication system  100  according to the first embodiment in that the switching hubs  1  include respective external CPUs  40 . The first switching hub  1 A includes the first input-output interface  10 A, the first external memory  20 A, the first switch IC  30 A, and a first external CPU  40 A as illustrated  FIG. 5 . The first external CPU  40 A is provided outside the first switch IC  30 A and is connected via a connecting line to the first switch IC  30 A. The first external CPU  40 A has a higher processing capacity than the first embedded CPU  31 A in the first switch IC  30 A. For example, it is preferable that the first external CPU  40 A have a higher clock frequency with which the corresponding CPU operates than the first embedded CPU  31 A, have a higher number of CPU cores than the first embedded CPU  31 A, and have a larger cache memory capacity than the first embedded CPU  31 A. 
     The second switching hub  1 B includes the second input-output interface  10 B, the second external memory  20 B, the second switch IC  30 B, and a second external CPU  40 B. The second external CPU  40 B is provided outside the second switch IC  30 B and is connected via a connecting line to the second switch IC  30 B. The second external CPU  40 B has a higher processing capacity than the second embedded CPU  31 B in the second switch IC  30 B. For example, it is preferable that the second external CPU  40 B have a higher clock frequency with which the corresponding CPU operates than the second embedded CPU  31 B, have a higher number of CPU cores than the second embedded CPU  31 B, and have a larger cache memory capacity than the second embedded CPU  31 B. 
     In the first and the second switching hubs  1 A and  1 B thus configured, the first external CPU  40 A reads setting information applicable thereto from the first external memory  20 A when the first switching hub  1 A is started up. If the first external CPU  40 A fails to read the setting information applicable thereto from the first external memory  20 A when the first switching hub  1 A is started up, the first external CPU  40 A transmits, to the second switching hub  1 B, a request frame F 1  indicating a request to transmit the setting information applicable thereto. Upon receiving the request frame F 1  from the first switching hub  1 A, the second external CPU  40 B of the second switching hub  1 B reads the setting information stored in the second external memory  20 B and applicable to the first switch IC  30 A. The second external CPU  40 B then transmits, to the first switching hub  1 A, a response frame F 2  containing the read setting information applicable to the first switch IC  30 A. The first external CPU  40 A in the first switching hub  1 A applies the applicable setting information to the first switch IC  30 A contained in the response frame F 2  transmitted from the second switching hub  1 B. As in the case of the vehicle communication system  100 B according to the third embodiment, the applicable setting information may be acquired by the corresponding external CPU  40 . 
     Modifications 
     Modifications of the embodiments are described next. An example in which the first and the second external memories  20 A and  20 B have the setting information applicable to all of the switches IC  30  included in the vehicle communication system  100  is described above. However, this example is not limiting. For example, the first external memory  20 A may be configured to store therein, out of the setting information applicable to all of the switches IC  30  included in the vehicle communication system  100 , the setting information applicable to some of those switches IC  30 . In that case, for example, the vehicle is configured to have the internal space thereof segmented into a plurality of regions. The regions include a unit region that includes two or more of the switching hubs  1 . Each of the switching hubs  1  included in this unit region stores therein the setting information applicable to that switching hub  1  and the other switching hub or hubs  1  in this unit region and does not store therein the setting information applicable to the other switching hubs  1  in the other region or regions. In one of the unit regions, for example, the first switching hub  1 A and the second switching hub  1 B are included. The first switching hub  1 A included in this unit region stores therein the setting information applicable thereto and to the second switching hub  1 B in this unit region and does not store therein the setting information applicable to the other switching hubs  1  in the other region or regions. This configuration can prevent capacities needed for the respective external memories  20  of the switching hubs  1  from being increased in the vehicle communication system  100 . 
     The present description illustrates an example in which the transfer unit is the switching hub  1  that transfers information to a specific port based on the routing table. However, this example is not limiting. For example, the transfer unit may be a hub that transfers information to all corresponding ports. 
     In a vehicle communication system according to the embodiments, when a transfer unit fails to acquire setting information applicable thereto from a storage section therein, the transfer unit is enabled to operate based on the setting information applicable thereto acquired from a storage section in another transfer unit, whereby the reliability of the vehicle communication system can be prevented from degrading. 
     Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.