Abstract:
A network system that comprises a plurality of communication apparatuses, each of the communication apparatuses being capable of performing a VLAN setting by using a VLAN number set for a connection port, that sets a VLAN number for each of the communication apparatuses, and that performs communication among cars of a train, wherein in a case where a specific type of packet that disables a VLAN setting is a packet of a multicast address, when a distribution target apparatus is connected to a communication apparatus that has received the specific type of packet, the communication apparatus transfers the specific type of packet to the distribution target apparatus and, irrespective of a VLAN number set for another communication apparatus, regards a VLAN different from a VLAN of the communication apparatus as a same network and transfers the specific type of packet to the another communication apparatus.

Description:
FIELD 
       [0001]    The present invention relates to a network system and a communication apparatus that perform communication by VLANs. 
       BACKGROUND 
       [0002]    Communication using VLANs (Virtual Local Area Networks) has been performed. In a system that shares a network, the VLANs can divide and use the network. For example, in a system in which a plurality of communication apparatuses (hubs) are connected, by performing VLAN settings on the connection ports of the communication apparatuses (the hubs), one network in physical arrangement can be logically operated as a plurality of networks. Such a technology is disclosed in Patent Literatures 1 to 3. 
         [0003]    CITATION LIST 
       Patent Literature 
       [0004]    Patent Literature 1: Japanese Patent Application Laid-Open No. 2007-5892 
         [0005]    Patent Literature 2: Japanese Patent Application Laid-Open No. 2003-198588 
         [0006]    Patent Literature 3: Japanese Patent Application Laid-Open No. 2004-72160 
       SUMMARY 
     Technical Problem 
       [0007]    However, according to the conventional technology, communication can be performed only in the network having the same VLAN setting. Therefore, there is a problem in that communication cannot be performed among communication apparatuses having different VLAN settings even if a plurality of communication apparatuses are connected. 
         [0008]    The present invention has been devised in view of the above, and it is an object of the present invention to obtain a network system and a communication apparatus that can perform communication among communication apparatuses having different VLAN settings. 
       Solution to Problem 
       [0009]    In order to solve the above problems and achieve the object, the present invention relates to a network system that comprises a plurality of communication apparatuses, each of the communication apparatuses being capable of performing a VLAN setting by using a VLAN number set for a connection port, that sets a VLAN number for each of the communication apparatuses, and that performs communication among cars of a train, wherein in a case where a specific type of packet that disables a VLAN setting is a packet of a multicast address, when a distribution target apparatus is connected to a communication apparatus that has received the specific type of packet, the communication apparatus transfers the specific type of packet to the distribution target apparatus and, irrespective of a VLAN number set for another communication apparatus, regards a VLAN different from a VLAN of the communication apparatus as a same network and transfers the specific type of packet to the another communication apparatus. 
       Advantageous Effects of Invention 
       [0010]    The network system according to the present invention attains an effect that it is possible to perform communication among communication apparatuses having different VLAN settings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a diagram illustrating a configuration example of a network system including communication apparatuses. 
           [0012]      FIG. 2  is a diagram illustrating the state of a normal network conforming to VLAN settings. 
           [0013]      FIG. 3  is a diagram illustrating the state of a network when a specific type of packet is used. 
           [0014]      FIG. 4  is a diagram illustrating the state of a network when the specific type of packet is used. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0015]    Exemplary embodiments of a network system and a communication apparatus according to the present invention are explained in detail below with reference to the drawings. Note that the present invention is not limited to the embodiments. 
       Embodiment 
       [0016]      FIG. 1  is a diagram illustrating a configuration example of a network system including communication apparatuses according to the present embodiment. Physical connections of apparatuses are shown. The network system includes communication apparatuses  1 ,  2 ,  3 , and  4 . The communication apparatuses  1  and  2  are connected by a Trunk Link  5 . The communication apparatuses  2  and  3  are connected by a Trunk Link  6 . The communication apparatuses  3  and  4  are connected by a Trunk Link  7 . 
         [0017]    A management apparatus  10  and apparatuses  11  to  13 , which are connected to the VLAN #1 setting ports, are connected to the communication apparatus  1 . Apparatuses  14  to  16 , which are connected to the VLAN #1 setting ports, are connected to the communication apparatus  2 . A management apparatus  20  and apparatuses  21  to  23 , which are connected to the VLAN #2 setting ports, are connected to the communication apparatus  3 . A management apparatus  30  and apparatuses  31  to  33 , which are connected to the VLAN #3 setting ports, are connected to the communication apparatus  4 . The communication apparatuses  1  to  4  each include a plurality of connection ports. The communication apparatuses  1  to  4  can perform VLAN settings by using VLAN numbers set for the connection ports. A specific example of the network system is a system in which, in a train formation, a communication apparatus in provided in each car and communication is performed among the cars by connecting the cars through Trunk Links. However, the network system is not limited to such communication among the cars. 
         [0018]      FIG. 2  is a diagram illustrating the state of a normal network conforming to VLAN settings. As shown in  FIG. 2 , the management apparatus  10  and the apparatuses  11  to  16  are connected to a network of a VLAN #1. Usually, the management apparatus  10  and the apparatuses  11  to  16  can perform communication only in the network set by this port VLAN #1. The management apparatus  20  and the apparatuses  21  to  23  are connected to a network of a VLAN #2. Usually, the management apparatus  20  and the apparatuses  21  to  23  can perform communication only in the network set by this port VLAN #2. The management apparatus  30  and the apparatuses  31  to  33  are connected to a network of a VLAN #3. Usually, the management apparatus  30  and the apparatuses  31  to  33  can perform communication only in the network set by this port VLAN #3. 
         [0019]    When communication is performed among cars, for example, a system is conceivable in which one communication apparatus is arranged in each of the cars and a VLAN is set for each of the cars. As an apparatus connected to each communication apparatus, there is a management apparatus that manages communication of a corresponding VLAN. As an apparatus connected to each communication apparatus, there are, for example, a guidance display apparatus, a destination display apparatus, and a sound data output apparatus. However, apparatuses connected to each communication apparatus are not limited to these apparatuses. 
         [0020]    Next, an explanation will be made of a case where communication is performed by a certain apparatus with apparatuses connected to communication apparatuses of other VLAN settings. Specifically, a microphone (an apparatus) connected to a communication apparatus of any car is used to output sound data from sound data output apparatuses connected to communication apparatuses of all cars in a train formation. When a certain apparatus performs communication with apparatuses connected to other VLANs, in the present embodiment, a specific type of packet is used. The specific type indicates a port number corresponding to “80” or “110” in TCP/UDP, an IP address, a MAC address, or the like. For example, when one apparatus transmits data to apparatuses connected to networks of VLANs having the same and different settings, the apparatus on the transmission side performs communication using a specific multicast address. When a multicast address is set as an IP address, a MAC address can also be determined. In each communication apparatus, passage permission is set in a table or the like included in its own apparatus in advance for the specific type of packet, whereby a packet for disabling the VLANs can be defined in the system. 
         [0021]      FIG. 3  is a diagram illustrating the state of a network when the specific type of packet is used. The state of the network in the case of multicast is explained. For example, when the apparatus  11  transmits data to the apparatuses connected to the networks of the VLANs having the same and different settings, the apparatus  11  transmits the specific type of packet in multicast. In this case, in the connection ports to which the apparatuses are connected, each communication apparatus sets passage permission for the multicast address. Multicast addresses permitted to pass are set in advance in each communication apparatus. Note that, in each communication apparatus, the multicast address is not permitted to pass through the connection port to which the management apparatus is connected. Consequently, in each communication apparatus, apparatuses connected to ports for which passage permission is set in advance can receive data in multicast. On the other hand, the management apparatuses cannot receive data in multicast according to a packet filtering function. 
         [0022]    Specifically, when the apparatus  11  communicates with the apparatuses  12  to  16  on the VLAN #1 side, the apparatuses  21  to  23  on the VLAN #2 side, and the apparatuses  31  to  33  on the VLAN #3 side, the apparatus  11  transmits the specific type of packet to the communication apparatus  1 . The communication apparatus  1  transfers the specific type of packet received from the apparatus  11  to the apparatuses  12  and  13  that are desired destinations and the communication apparatus  2 . The communication apparatus  2  transfers the specific type of packet received from the communication apparatus  1  to the apparatuses  14  to  16  that are desired destinations. Moreover, irrespective of the setting of the port VLANs (ignoring the setting of the port VLANs), the communication apparatus  2  transfers the specific type of packet received from the communication apparatus  1  to the communication apparatus  3 . Irrespective of the setting of the port VLANs (ignoring the setting of the port VLANs), the communication apparatus  3  transfers the specific type of packet received from the communication apparatus  2  to the apparatuses  21  to  23  that are desired destinations and the communication apparatus  4 . Irrespective of the setting of the port VLANs (ignoring the setting of the port VLANs), the communication apparatus  4  transfers the specific type of packet received from the communication apparatus  3  to the apparatuses  31  to  33  that are desired destinations. 
         [0023]    As explained above, when receiving the specific type of packet from the apparatus  11 , the communication apparatuses  3  and  4  disable the settings of the port VLANs and operate while regarding the networks of the VLAN #2 and the VLAN #3, respectively, as the same network as the VLAN #1. 
         [0024]    Note that communication among the VLANs is not limited to multicast and can also be performed in unicast.  FIG. 4  is a diagram illustrating the state of a network when the specific type of packet is used. The state of the network in the case of unicast is explained here. For example, when the apparatus  11  transmits data to the apparatus  31  connected to the network of the VLAN having a different setting, the apparatus  11  transmits the specific type of packet in unicast. In this case, as explained above, in the connection ports to which the apparatuses are connected, each communication apparatus sets passage permission for the unicast address. Unicast addresses permitted to pass are set in advance in each communication apparatus. 
         [0025]    Specifically, when the apparatus  11  communicates with the apparatus  31  on the VLAN #3 side, the apparatus  11  transmits the specific type of packet to the communication apparatus  1 . The communication apparatus  1  transfers the specific type of packet received from the apparatus  11  to the communication apparatus  2 . Irrespective of the setting of the port VLANs (ignoring the setting of the port VLANs), the communication apparatus  2  transfers the specific type of packet received from the communication apparatus  1  to the communication apparatus  3 . Irrespective of the setting of the port VLANs (ignoring the setting of the port VLANs), the communication apparatus  3  transfers the specific type of packet received from the communication apparatus  2  to the communication apparatus  4 . Irrespective of the setting of the port VLANs (ignoring the setting of the port VLANs), the communication apparatus  4  transfers the specific type of packet received from the communication apparatus  3  to the apparatus  31  that is a desired destination. 
         [0026]    As in the case of multicast, when receiving the specific type of packet from the apparatus  11 , the communication apparatuses  3  and  4  disable the settings of the port VLANs and operate while regarding the networks of the VLAN #2 and the VLAN #3, respectively, as the same network as the VLAN #1. 
         [0027]    As explained above, according to the present embodiment, in a network system configured from a plurality of communication apparatuses, irrespective of the VLAN settings, a communication apparatus that has received a specific type of packet regards a plurality of VLANs as the same network and transfers the received packet to apparatuses that are connected to the connection ports and are desired destinations and adjacent communication apparatuses. Consequently, in a system that shares a network, it is possible to perform communication among networks having different VLAN settings. 
       REFERENCE SIGNS LIST 
       [0028]      1 ,  2 ,  3 ,  4  communication apparatus,  5 ,  6 ,  7  Trunk Link,  10 ,  20 ,  30  management apparatus,  11  to  16 ,  21  to  23 ,  31  to  33  apparatus.