Abstract:
The network switching system is provided with a communication route management table for managing transmission path information of a wireless network including wireless access devices, and a connection device management table for managing, in common on the wireless network, the information on wireless network devices connected to the wireless access devices. The system is further provided with a signal transmitter for referencing the two tables, and generating a signal frame depending on the destination of communication signals received to transmit the signal frame generated. Communication is prevented from being interrupted when communication route information is updated, and from being invaded on a communication route in the network. The network system is more efficiently utilized.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a network switching system, and more particularly to a network switching system applicable to a wireless or mobile network system. 
     2. Description of the Background Art 
     In a wireless network system, for example, access control between plural wireless network devices is managed by a wireless access device, called as access point-device. In general, the access point device is disposed on a wired network for connection to an external network or to other access point devices. Hence, there was raised a problem that no access point devices may be provided under the situation, for example, where a wired network cannot-be laid, with the result that it is not possible to construct a wireless network connectable to an external network. 
     For overcoming this inconvenience, a wireless mesh network has now been proposed, in which a plurality of access point devices are arranged in the form of meshes, and are interconnected by wireless channels with the connections implemented by wired circuits minimized so as to attain a broader service area connectable to the network, as taught by Japanese patent laid-open publication No. 2005-184522. 
     In a wireless network, in order to set up both-way transmission between plural wireless network devices, it is necessary to determine a transmission path between the devices. The conventional methods of determining transmission paths between wireless network devices include, for example, ones based upon a proactive OLSR (Optimized Link State Routing) protocol or a reactive AODV (Ad hoc On-demand Distance Vector) protocol, which are respectively taught by Toshio KOIDE, “Sixth OLSR (Optimized Link State Routing) protocol,” and Toshio KOIDE, “Seventh AODV (Ad hoc On-demand Distance Vector) protocol.” 
     However, with the conventional method of deciding transmission paths, all the devices included in a network are possibly involved in a transmission path. That causes not only the access point devices but also the wireless network devices to be possibly involved in the transmission path. 
     For example, when a wireless network or mobile device moves, an access point device to be connected maybe replaced. If an access point is added or removed, then information on transmission paths may be updated accordingly. In addition to that, information on transmission paths for the wireless network devices provided at a distal end also has to be updated. That may cause transmission to be temporarily interrupted. 
     In general, a wireless mesh network is structured with either one of the two features: (a) each access point device forms a particular network separate in segment from others, and (b) a network formed between a wireless network device and an access point device is common to a network formed between access point devices. 
     However, with a network structured with the feature (a), when a wireless network or mobile device moves from one access point device interconnected thereto to a service area covered by another access point device, the wireless network device has to update data of the IP address stored to that of the other access point device, with the result that the network connection is interrupted and will not be available until a network connection is re-established. 
     On the other hand, in a network structured with the feature (b), plural networks co-exist each of which conveys a particular sort of communication different from each other in characteristics, such as speed of transmission or strength of the electrical field. Usually, efficient utilization of a certain network requires various parameters thereof to be tuned. Where plural sorts of networks co-exist as with the feature (b), the situation becomes more complex to the extent that it is difficult to select optimum parameters, thus deterring the efficient use of the network. 
     There is also raised a security-related problem that, communication between wireless network devices allows other, strange radio network devices to readily monitor transmission paths between the access point devices in the wireless network. 
     For these reasons, there has been raised a demand for a network switching system, in which communication may be carried out without being affected by settings of remote devices on communication between wireless network devices or between access points, and communication protocols or standards, aiming at preventing disconnection of transmission otherwise caused by updating transmission path information resultant from addition or removal of an access point device or movement of a wireless network device from one to another service area, and invasion into a transmission path from strange mobile devices, as well as achieving more efficient utilization of the network system. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved network switching system capable of efficiently utilizing network resources. 
     The present invention provides, in its first aspect, a network switch apparatus comprising a communication route management table for managing communication route information on a wireless network, the wireless network including a plurality of wireless access devices, a connection device management table for managing, in common on the wireless network, information on wireless network devices to be connected to the wireless access devices, and a signal transmitter for referencing the connection device management table and the communication route management table and to generate a signal frame depending on a destination to which a communication signal received is destined, and for transmitting the generated signal frame. 
     The present invention also provides, in its second aspect, a method of switching a wireless network, comprising the steps of preparing a communication route management table for managing communication route information of a wireless network, the wireless network including a plurality of wireless access devices, preparing a connection device management table for managing, in common on the wireless network, information on wireless network devices to be connected to the wireless access devices, and referencing the connection device management table and the communication route management table to generate a signal frame depending on a destination to which a communication signal received is destined, and transmitting the signal frame generated. 
     The present invention also provides, in its third aspect, a wireless access device including the network switch apparatus in accordance with the first aspect of the invention, the wireless access device performing access control with a communication layer with the wireless access devices other than the wireless access device in which the apparatus is included separate from a communication layer with the wireless network devices connectable to the wireless access device in which the apparatus is included. 
     The present invention also provides, in its fourth aspect, a wireless network system including a plurality of wireless access devices each connectable to a wireless network device, wherein the wireless access device is defined by the third aspect of the invention. 
     With the network switching system according to the present invention, the communication layer for communication between wireless access devices and the communication layer for communication between wireless network devices may be handled separately from each other. It is therefore possible to prevent communication from being disconnected, which would otherwise be caused by updating the communication route information, and to prevent a communication route in the communication network from being invaded. Also, the resources of the network system is more efficiently utilized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and features of the present invention will become more apparent from consideration of the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic block diagram showing a simplified model of a wireless local area network (LAN) system with an inner structure of the wireless LAN access points depicted according to an embodiment of the present invention; 
         FIG. 2  is a diagrammatic view showing exemplary items and contents of a routing table included in the illustrative embodiment shown in  FIG. 1 ; 
         FIG. 3  is also a diagrammatic view showing exemplary items and contents of a MAC (Media Access Control) address management table of the illustrative embodiment; 
         FIG. 4  shows in a diagrammatic view an exemplified configuration of the wireless LAN system of the embodiment together with specific contents of the tables owned by the access points; 
         FIG. 5  shows an example of formats of data frames of the embodiment; 
         FIG. 6  is a flowchart useful for understanding the operation of the access point of the embodiment; 
         FIG. 7  is a schematic view useful for understanding how the communication operation proceeds between the access points of the embodiment; 
         FIG. 8  schematically shows the network structure of the embodiment; 
         FIG. 9  is a flowchart useful for understanding the operation of the access point when a new access point is involved; 
         FIG. 10  is a flowchart useful for understanding the operation of the access point when the MAC address management table is updated; and 
         FIG. 11  exemplarily shows the MAC address management table, after updated. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings, a preferred embodiment of the network switching system applied to a wireless network in accordance with of the present invention will be describe in detail. With the illustrative embodiment, a wireless access apparatus in accordance with the invention is applied to a wireless local area network (LAN) access point device contained in a LAN system formed into a wireless mesh network. 
       FIG. 1  depicts a simplified configuration of a wireless LAN system  1  including wireless LAN access point devices  2  with the inner structure thereof specifically illustrated. The wireless LAN system  1  of the present embodiment is formed into a wireless mesh network in which plural wireless LAN access point devices, sometimes referred to below simply as access points,  2 , are arranged in meshes. Across these access points, communication is established by wireless transmission. 
     As seen from  FIG. 1 , the wireless LAN system  1  of the embodiment comprises plural access point devices  2 , specifically shown with reference numerals  2 - 1 ,  2 - 2  and  2 - 3 . The access point devices  2 - 1  and  2 - 3  have wireless communication with plural wireless LAN devices  3 - 1  and  3 - 3  staying in the respective service areas which allow for communication therewith. It is noted that  FIG. 1  shows a highly schematic network configuration for the wireless LAN devices  3 - 1  and  3 - 3  to communicate with each other. Hence, on a transmission path  4  between the access points  2 - 1  and  2 - 3 ,  FIG. 1  simply shows only one access point  2 - 2  involved for relaying between the access points  2 - 1  and  2 - 3 . However, there may of course be involved plural intervening access points on the transmission path  4 . 
     The access points  2 - 1 ,  2 - 2  and  2 - 3 , generally designated with the reference numeral  2 , are adapted to transmit a beacon signal at predetermined time intervals. Corresponding one of the wireless LAN devices  3 - 1  and  3 - 2 , when having received the beacon signal, transmits a signal toward that access point  2  in response. The wireless LAN devices, or mobile devices,  3 - 1  and  3 - 2  will sometimes correspondingly designated with the general reference numeral  3 . The access point  2  in turn receives the signal from the wireless LAN device  3  to detect that the wireless LAN device  3  to connect stays in its service area, thus performing access control for the wireless transmission of the wireless LAN device  3 . 
     The access point  2  has the function of acquiring a MAC address contained in the header information of a signal, specifically a MAC frame, received from the wireless LAN device  3  connected thereto to manage the MAC address. As will be described in detail subsequently in connection with the manner of managing the MAC address by the access point  2 , this MAC address is made associated with an IP (Internet Protocol) address of the access point  2  in question. In order that information defining the relationship of the IP address of the access point device in question  2  with the MAC address of the wireless LAN device  3  connected thereto is made commonly owned by all other access point devices located on the wireless LAN system  1 , the access point in question  2  transfers that information to nearby access points  2  positioned therearound. 
     There are a variety of methods of making such information commonly owned by the totality of the access points  2 . With the illustrative embodiment, the access point device  2  makes use of the flooding function. The flooding function is of unanimously distributing the same information to all access points. The flooding function may be implemented by a variety of methods, based upon the OLSR or AODV protocol stated earlier. The invention is not limited to the two methods but any other methods may be used insofar as they allows tables defining the above-mentioned information to be delivered to all the access points  2 . 
     As seen from  FIG. 1 , the access points  2 - 1  and  2 - 3 , respectively include wireless LAN transceivers  21 - 1  and  21 - 3 , for wireless mesh network side, inter-access-point (AP) virtual LAN switches  22 - 1  and  22 - 3 , and other wireless LAN transceivers  23 - 1  and  23 - 3  for wireless LAN device side, which are interconnected as illustrated. With the illustrative embodiment, the access points  2 - 1 ,  2 - 2  and  2 - 3  have the same structure as each other. Hence, when description is made on the configuration or operation of those devices  2 - 1 ,  2 - 2  and  2 - 3 , common to each other, the numerals following the hyphens of those reference numerals designating the devices  2 - 1 ,  2 - 2  and  2 - 3  and the structural elements included therein will be dispensed with for convenience. For example, the LAN transceivers  21 - 1 ,  21 - 2 , not shown, and  21 - 3  are sometimes represented by the reference numeral  21 . 
     The wireless mesh network side LAN transceiver, referred to below as network side transceiver,  21  is adapted to receive communication data, or MAC frame, transmitted from another access point  2  in accordance with a communication system or scheme prescribed on the network, and transfer the so received communication data to the inter-AP virtual LAN switch  22 . The network side transceiver  21  is also adapted to receive communication data from the inter-AP virtual LAN switch  22  to transmit the communication data in accordance with the prescribed communication system. 
     The inter-AP virtual LAN switch  22  is adapted to virtually establish a full mesh network to another access point  2  connected to the wireless mesh network, and adjusts the structure of a data frame of communication data so as to enable interconnection to the access point  2 . 
     The inter-AP virtual LAN switch  22  at least includes the frame recognizing function of recognizing the destination of transmission, based on the header information of the received communication data, or MAC frame. The LAN switch  22  further includes the function of determining, when the transmission is destined to another wireless LAN or mobile device  3 , which access point  2  is connected to the other wireless LAN device  3  to which the communication data to be transmitted is destined, and the frame formulating function of formulating a frame of communication data for enabling the data to be transmitted to the access point  2  thus determined. The LAN switch  22  also includes the function of transmitting the communication data of the frame formulated, and the table update function of updating the tables, as will be described subsequently. 
     The inter-AP virtual LAN switch  22  includes a routing table  22 A and a MAC address management table  22 B, and is adapted to use at least these two tables  22 A and  22 B to formulate a data frame. This establishes a virtual network to accomplish communication between the two access points  2 . 
     The routing table  22 A contains information on transmission paths, or communication routes, interconnecting the access points  2  included in the wireless mesh network  1 . To the routing table  22 A, applicable is a routing table specifically formulated on a particular access point  2 . There is therefore how to formulate the routing table  22 A is not particularly limited to but may be specific to the access point  2 . As an exemplary method of formulating the routing table  22 A, it may be advisable to use e.g. an OLSR or AODV protocol stated earlier. 
     The MAC address management table  22 B contains management information on which of the access points  2  the wireless LAN device  3  is in connection with. The address management table  22 B is owned in common by all of the access points  2  on the wireless LAN system  1 . This table, owned in common by all access points  2 , may be prepared in such a manner that the access point  2 , when having detected a connection to the wireless LAN or mobile device  3 , floods the information correlating the MAC address of that wireless LAN device  3 , connected thereto, with the IP address of the device in question  2 , and then all the remaining access points  2  formulate and update the MAC address management table  22 B thereof. 
       FIG. 2  shows exemplary items and contents of the routing table  22 A, which is owned by the access point  2 - 1 . As seen from the figure, the items of the routing table  22 A of the present embodiment include, for example, the identification (ID) information  101  on the access point  2  of a destination, the interface information  103  and the device identification information  105  for relaying to the access point  2  of the destination. 
     For example, the first line  107  of the exemplary contents of  FIG. 2  stands for a case where the destination of transmission of transmission data is the access point  2 - 2 . In that case, there is indicated the IP address of the access point  2 - 2  in the identification information column  101  for the destination access point, while there is indicated the network side transceiver  21 - 1 , in the interface information column  103 , by way of the routing information. Thus, the AP-side virtual LAN switch  22 - 1  references this routing information  107 , and donates the transmission data to the network side transceiver  21 - 1  in order to send out the transmission data to the access point  2 - 2 . 
     The second line  107  of the exemplary contents of  FIG. 2  stands for a case where transmission data are destined to the specific access point  2 - 3 . In the instant case, there are indicated, by way of the routing information, the IP address of the network side LAN transceiver  21 - 3  of the access point  2 - 3 , the network side transceiver  21 - 1  and the IP address of the access point  2 - 2 , in the columns  101 ,  103  and  105 , respectively, of the identification information of the destination access point, the interface and the relay device identification information. The inter-AP virtual LAN switch  22 - 1  references this routing information. In order to send transmission data to the network side transceiver  21 - 3  of the access point  2 - 3 , the transmission data need to initially be transmitted to the access point  2 - 2 . Therefore, the inter-AP virtual LAN switch  22 - 1  sends the data for transmission to the network side transceiver  21 - 1 , in order to transmit the data to the access point  2 - 2 . 
       FIG. 3  illustrates exemplary items and contents of the MAC address management table  22 B. For example, the items of the MAC address management table  22 B in  FIG. 3  include the MAC addresses  111 , allocated to the wireless LAN device  3 , and the connection access point identification information  113 . It is also seen from  FIG. 3  that the wireless LAN devices  3 - 1  and  3 - 3  are connected to the access points  2 -land  2 - 3 , respectively. On the table  22 B shown in  FIG. 3 , the information  113  for identifying the connection access points represents the name of the access points  2 . However, the IP address of the access points  2  may instead be used as the identifying information  113  provided that the IP address is able to identify a specific access point  2  connected to the wireless LAN device  3 . In an application where the identification information of an access point to be connected is the name of that access point, the IP address of that access point may be acquired by making an inquiry to e.g. a domain name server (DNS) of the Internet. 
     The wireless LAN device side wireless LAN transceiver  23 , similarly referred to below as a device side transceiver  23 , is adapted to receive communication data, transmitted from the wireless LAN device  3  in accordance with the communication system specific to the network, and transfer the so received communication data to the inter-AP virtual LAN switch  22 . The device side wireless LAN transceiver  23  is also adapted to receive communication data from the inter-AP virtual LAN switch  22  and transmit the thus received communication data in accordance with the communication system. Although there is no limitation to the wireless transmission system applicable to the device side wireless LAN transceiver  23 , the communication system prescribed by e.g. IEEE (Institute of Electrical and Electronics Engineers) 802.11, such as IEEE 802.11a, 802-11b or 802-11g, may be used. 
     The wireless LAN devices  3 - 1  and  3 - 3 , generally designated with the reference numeral  3 , is a mobile wireless communication terminal unit adapted to establish transmission via the access point  2  in accordance with the communication system specific to the network To the wireless LAN device  3 , any device is broadly applicable which has a prescribed wireless communication function that may be implemented by, for example, a mobile communication or terminal device, such as a note book personal computer, a mobile data terminal, a mobile phone subscriber set, a PHS (Personal Handy Phone System) terminal or a PDA (Personal Digital Assistant) having a wireless LAN card or circuit board adapted for coping with IEEE 802.11, such as IEEE 802.11a, 802-11b or 802-11g. 
     In distinction from the state-of-art devices, the wireless LAN device  3  does not include a routing table. The reason is that the access point  2  includes the routing table  22 A and the MAC address management table  22 B, and uses these two tables to construct two networks, namely a device side network and an AP side network. More specifically, when the wireless LAN devices  3  communicate with each other, the present embodiment is adapted in such a fashion that the access point  2  to which the wireless LAN device  3  serving as the source of transmitting data is connected uses or references the routing table  22 A and the MAC address management table  22 B to specify the wireless LAN device  3  to which the data are to be destined. 
     In operation, referring first to  FIG. 4 , with the exemplified wireless LAN system  1 , having the three access points  2 - 1 ,  2 - 2  and  2 - 3 , communication will be established between the wireless LAN devices  3 - 1  and  3 - 3  in a manner to read below. As shown in the figure, the access point (AP 1 )  2 - 1  has its IP address and MAC address represented by IP_AP 1  and MAC_AP 1 , respectively, and the access point (AP 2 )  2 - 2  has its IP address and MAC address represented by IP_AP 2  and MAC_AP 2 , respectively. The IP address and the MAC address of the access point (AP 3 )  2 - 3  are IP_AP 3  and MAC_AP 3 , respectively. 
     In addition, the IP address and the MAC address of the wireless LAN device (CL 1 )  3 -l are IP_CL 1  and MAC_CL 1 , respectively, and the IP address and the MAC address of the wireless LAN device (CL 2 )  3 - 2  are IP_CL 2  and MAC_CL 2 , respectively. The wireless LAN device (CL 3 )  3 - 3  has its IP address and MAC address of IP_CL 3  and MAC_CL 3 , respectively. 
     Further, the access points  2 - 1 ,  2 - 2  and  2 - 3  respectively have routing tables  22 A- 1 ,  22 A- 2  and  22 A- 3 . Each routing table  22 A contains, as shown in  FIG. 4 , the destination IP address  101  of the other access points  2  to be destined, the interface  103  associated with the access point  2  serving as the source of transmission in connection with the access point to be destined, and a gateway identification  105  representing the IP address of the access point  2  serving as a gateway interconnecting the destination and source sides of the access point in question  2 . In addition, the access points  2  have the MAC address management table  22 B which includes the MAC address  111  of the wireless LAN devices and the IP address  113  of the access point  2  to which the wireless LAN device  3  in question is connected. 
     In the network system  1  shown in  FIG. 4 , the wireless LAN device  3 - 1  formulates a data frame, and modulates wireless signals with the so formulated data frame at a predetermined frequency to transmit the resulting signals in the form of electro-magnetic waves. Although a variety of communication systems may be used for the wireless communication system for transmission between the wireless LAN device  3 - 1  and the device side wireless LAN transceiver  23 - 1 , the communication system may preferably be used which is prescribed by IEEE 802.11, such as IEEE 802.11a, 802.11b or 802.11g. 
       FIG. 5 , part (A), schematically depicts an exemplary configuration of a data frame  119  formulated by the wireless LAN device  3 - 1 . The exemplary configuration or format of the data frame  119  in the wireless LAN device  3 - 1  shown in  FIG. 5 , part (A), may be divided into a data field  121  and a header field  123 . As seen from the figure, the header field  121  comprises the subfields of the destination MAC address  125 , the MAC address of the source of transmission  127 , the destination IP address  129  and the IP address of the source of transmission  131 . In the present embodiment, the header field  123  is termed the device side network header information. When the wireless LAN device  3 - 1  transmits data to the wireless LAN device  3 - 3 , the device  3 - 1  formulates the data frame  119  with its header  123  containing the destination MAC address  125  of MAC_CL 2 , the source MAC address  127  of MAC_CL 1 , the destination IP address  129  of IP_CL 3  and the source IP address of IP_CL 1 , as exemplarily depicted. 
     The wireless signals, transmitted from the wireless LAN device  3 - 1 , are captured by the device side transceiver  23 - 1  of the access point  2 - 1 . This is shown in  FIG. 6  as step S 1 , which figure is a flowchart showing the operation in the access point  2 . 
     On receipt of the wireless signals, the device side wireless LAN transceiver  23 - 1  takes out the destination MAC address (MAC_CL 3 )  125  and the Source MAC address (MAC_CL 1 )  127 , contained in the received signal, and delivers the destination MAC address  125  and the Source MAC address  127  to the inter-AP virtual LAN switch  22 - 1 . The inter-AP virtual LAN switch  22 - 1  refers to the address management table  22 B to take out the identification information of the access point relating to the destination MAC address  125 . In short, the access point  2 - 3  is decided to which the wireless LAN device  3 - 3  is to be connected, step S 2 . 
     Since the MAC address management table  22 B is owned in common by the totality of the access points  2 , architecting the wireless LAN system  1 , the access point  2 - 1  to which the wireless LAN device  3 - 1  functioning as the source of transmission is connected can determine the access point  2 - 3  which the wireless LAN device  3 - 3  serving as the destination of transmission is connected to. 
     When the inter-AP virtual LAN switch  22 - 1  has decided on the access point  2 - 3  as the destination of transmission, the inter-AP virtual LAN switch  22 - 1  acquires, based on the routing table  22 A- 1 , the routing information for transmission to the access point  2 - 3  as the destination of transmission, step S 3 . 
     Upon acquisition of the routing information on the path to the access point  2 - 3  serving as the destination of transmission, the inter-AP virtual LAN switch  22 - 1  accords a header  133 , derived from the routing information, to the communication data  119 , step S 4 , to formulate a data frame  135 . 
       FIG. 5 , part (B- 1 ), shows an exemplary structure of the data frame  135  formulated by the inter-AP virtual LAN switch  22 - 1 . As shown in part (B- 1 ), the inter-AP virtual LAN switch  22 - 1  further appends the AP side network header information  133  to the data frame  119 , in order to render possible the communication across the access points  2 . Based on the routing table  22 A- 1 , the inter-AP virtual LAN switch  22 - 1  formulates the data frame  135  to be sent to the access point  2 - 3  serving as the destination of transmission with the header  133  attached to the data frame  119  transmitted from the access point  2 - 1  to the access point  2 - 2 . The header  133  includes, as illustrated, the fields of the destination MAC address  137  of MAC_AP 2 , the source MAC address  139  of MAC_AP 1 , the destination IP address  141  of IP_AP 3  and the source IP address  143  of IP_AP 1 . 
     When the data frame  135  has been formulated by the inter-AP virtual LAN switch  22 - 1 , the so formulated data frame is sent to the network side transceiver  21 - 1 , which then transmits the data frame  135  in accordance with the communication system of the network system, step S 5 . 
     Specifically, when data to be transmitted between the wireless LAN devices  3 - 1  and  3 - 3  are transmitted or relayed between the access points  2 , the inter-AP virtual LAN switch  22 - 1  of the access point  2 - 1 , serving as a source of transmission, formulates the data frame  135 , obtained by wrapping the MAC frame  119 ,  FIG. 5 , part (A), transmitted between the wireless LAN devices  3  with a frame of another communication layer, and transmits the data frame  135  so wrapped. 
     The communication data  135 , transmitted from the access point  2 - 1 , is in turn received by the network side transceiver  21 - 2  of the access point  2 - 2  in the example. In the network side transceiver  21 - 2 , the AP side network header information  133 , contained in the header information of the communication data  135 , is taken out and delivered to the inter-AP virtual LAN switch  22 - 2 . The inter-AP virtual LAN switch  22 - 2  uses the AP side network header information to reference the routing table  22 A- 2 . For transmitting the data frame  135 , transmitted from the access point  2 - 1 , to the access point  2 - 3 , the inter-AP virtual LAN switch  22 - 2  formulates, based on the routing table  22 A- 2 , a data frame  145  having its header  145  substituted. In the header  147 , as shown in part (B- 2 ), the destination MAC address  149  is MAC_AP 3 , the source MAC address  151  is represented by MAC_AP 2 , the destination IP address  153  is IP_AP 3  and the source IP address  155  is IP_AP 1 . The resulting communication data  145  will be transmitted to the network side transceiver  21 - 2 . The network side transceiver  21 - 2  sends out the thus formulated data frame  145  to the access point  2 - 3  over the wireless medium. 
     The data frame  145 , thus transmitted from the access point  2 - 2 , is received by the network side transceiver  21 - 3  of the access point  2 - 3 . From the data frame  145 , received by the network side transceiver  21 - 3 , the header information  147  is taken out by the network side transceiver  21 - 3  and sent to the inter-AP virtual LAN switch  22 - 3 . Based on the AP side network header information  147 , the inter-AP virtual LAN switch  22 - 3  verifies the data to be data addressed to the device in question  2 - 3 , and accordingly takes in the communication data  145 . 
     When the communication data  145  have been taken in by the inter-AP virtual LAN switch  22 - 3 , the inter-AP network header information, contained in the header information field  147 , is separated from the header information field  147  by the inter-AP virtual LAN switch  22 - 3 , and the resulting communication data  119  are sent to the device side wireless LAN transceiver  23 - 3 . That is, the communication data of the data frame  119 , shown in part (A), is sent to the device side wireless LAN transceiver  23 - 3 . 
     The device side wireless LAN transceiver  23 - 3  transmits the communication data  119 , supplied thereto from the inter-AP virtual LAN switch  22 - 3 , to the wireless LAN device  3 - 3 , in accordance with the communication system prescribed in the network, such as IEEE 802.11, such as IEEE802.11a, 802.11b or 802.11g, in order to deliver the communication data  119  to the latter device  3 - 3 . 
     Thus, the device side network header information  133 , different from that used in the transmission between access points, or AP side header information,  123  is added to the data frame  119  for transmission. That causes, as shown for example in  FIG. 7 , the two wireless LAN devices  3 - 1  and  3 - 2  connected to each other to virtually view the communication established between the access points  2 - 1  and  2 - 3  in the form of wired LAN. 
     If the access points performing the function and operation stated above are arranged in multiple as shown in  FIG. 8 , for example, the resultant network configuration will be made up by access points  2 - 4  through  2 - 8  and the wireless LAN devices  3 - 4  through  3 - 9 , which are interconnected as illustrated. In the network, there are two different sub-networks, namely an access point side sub-network  161  for dealing with communication between the access points  2 - 4  through  2 - 8 , and a device side sub-network  163  for handling communication between the access points  2 - 4  through  2 - 8  and the wireless LAN devices  3 - 4  through  3 - 9 , for example. The two sub-networks  161  and  163  are thus interconnected with each other to carry out communication operations. 
     The access points  2  will operate, when one access point  2  is newly added to the wireless LAN system  1 , as described below.  FIG. 9  shows how data are transmitted between an existing access point  22 - 11  and another access point  2 - 10 , when newly added in the neighbor of the former. When the access point  2 - 10  is added on the wireless LAN system  1 , the network side transceiver  21 - 10  of the access point  2 - 10  periodically transmits control information to accord the control information to the access points  2  neighboring thereto, step S 11 . This control information is of distributing information owned by the access point, and may include e.g. a HELLO message. In this manner, the neighboring access points may be advised of the fact of the addition of the new access point. 
     When the neighboring access point  2 - 11  receives the control information, transmitted from the access point  2 - 10 , the neighboring access point device  2 - 11  adds, based on the so received control information, the information pertinent to the access point  2 - 10  to a routing table  22 A- 11  of the access point  2 - 11  of the device in question  2 - 11 , step S 12 . 
     Also, the neighboring access point  2 - 11  periodically transmits the control information. The access point  2 - 10  captures the control information transmitted from the neighboring access point  2 - 10  to formulate a routing table  22 B- 10  of the access point device in question  2 - 10  in accordance with a prescribed protocol for preparation of the routing table, such as OLSR protocol or AODV protocol RIP, steps  13  and  14 . 
     The neighboring access point  2 - 11  also transmits data of its MAC address management table  22 B to the access point  2 - 10 , step S 15 . The access point  2 - 10 , having received the data of the MAC address management table  22 B, is able to utilize the data of the MAC address management table  22 B owned in common by the access points  2  on the wireless LAN system  1 , step S 16 . 
     The neighboring access point  2 - 11  updates its routing table  22 A- 11 , and further notifies the remaining access points of that effect. That causes the totality of the access points  2  on the network  1  to co-own the information. Thus, when the addition of an access point causes a transmission path to be shortened, the shortened path may be determined by and available to the access points in connection therewith. 
     In  FIG. 9 , the control information and the MAC address management table data are separately shown from each other in steps S 13  and S 15 . However, the system may be adapted such that the control information includes the information pertinent to the MAC address management table  22 B. In addition, so far as the routing table  22 A and the MAC address management table  22 B are updatable, steps S 14  and step S 15  may be processed in a reversed order. 
     Not only the addition but also the deletion of the access point  2  may be dealt with by the operation similar to that described above. 
     The MAC address management table  22 B, co-owned by the access points  2  on the wireless LAN system  1 , may be updated in the manner that will be described with reference to  FIG. 10 . The MAC address management table  22 B is updated, for example, when the wireless LAN device  3  moves from the service area, or communication sphere, of one of the access points  2  to which the wireless LAN device  3  has been connected to that of another of the access points  2 . 
       FIG. 10  illustrates the updating operation of the MAC address management table  22 B in the access point  2 . Initially, the wireless LAN or mobile device  3  moves out of the communication sphere covered by the access point  2  to which it has been connected into the communication sphere of another access point  2  to which the wireless LAN device  3  is to be connected. In general, the wireless LAN device  3  is adapted to receive beacon signals, periodically transmitted by the access point  2 , to identify that particular access point  2 . For example, the wireless LAN device  3  is adapted for determining one of the access points  2  which has transmitted the beacon signal shaving its reception strength highest among them as a new access point device to be connected in wireless. 
     When the wireless LAN device  3  has moved into the communication sphere of the new access point  2 , this new access point  2  receives the signal transmitted from the wireless LAN device  3  to detect the-wireless LAN device  3 . 
     Upon detection of the wireless LAN device  3 , the new access point  2  acquires the MAC address of the wireless LAN device  3 , from the signal received from the wireless LAN device  3 , step S 22 . The access point  2  then transmits the information, including the MAC address of the wireless LAN device  3  and the IP address of the own access point  2 , to the neighboring access points  2 , step S 23 . 
     Also, the new access point  2  updates its MAC address management table  22 B such that the IP address of that access point is correlated with the MAC address of the wireless LAN device  3 , step S 24 . 
     Between the remaining access points  2 , this update information is transmitted, so that these access points  2  will update their MAC address management tables  22 B. 
     With reference to  FIGS. 3 and 11 , it will be described how the MAC address management table  22 B is updated when the wireless LAN device  3 - 3 ,  FIG. 1 , has moved so as to be allowed to connect to the access point  2 - 2 . By way of example, the contents of the MAC address management table  22 B, before updated, are shown in  FIG. 3 . When the wireless LAN device  3 - 3  moves, the MAC address management table is updated from the state shown in  FIG. 3  to the state shown in  FIG. 11 , causing the MAC address of the wireless LAN device  3 - 3 , thus having moved, to be in keeping with the access point  2 - 2 . 
     As described above, the MAC address management table  22 B is updated, and the MAC address management table  22 B thus updated is used to establish data communication for the wireless LAN device  3 . 
     With use of the access points  2  of the instant embodiment, described above, the following advantages are achieved. With the illustrative embodiment, in which there are provided the MAC address management table  22 B, owned in common by the access points  2  on the network  1 , and the routing table  22 A for routing the access points  2 , the access point  2  connected to the wireless LAN device  3  of the destination is able to recognize or determine a transmission path to the wireless LAN device  3  of the destination and the access point  2  associated therewith. 
     Hence, when the access point  2  is dynamically added or deleted, or the transmission path is changed as a result of movement of the wireless LAN device  3 , the update of the routing table contained in the wireless LAN devices at the distal end as done with the conventional system is not required, thus eliminating temporary interruption or disconnection of the communication otherwise encountered at the time of updating the transmission path. 
     Moreover, with the present embodiment, it is possible, with use of the two sorts of tables, namely the MAC address management table  22 B and inter-AP routing table  22 A, to carry out the communication in such a manner that the AP side network and the device side network will operate as different networks from each other. 
     Thus, in carrying out communication between the wireless LAN devices  3 , the transmission path between the access points may be shielded from others, with the consequence that the path of possible invasion by a third party into the inside of the network between the access points  2  may be decreased to improve the security. 
     Since the networks may be made distinct or separate from each other, communication parameters, such as the optimum transmission rate or the electrical field strength, may be set independently, so that the respective networks will be of different characteristics, thereby enhancing the network utilization efficiency. 
     Moreover, with the illustrative embodiment, in which the access points  2  own the MAC address management table  22 B in common, when the movement of the wireless LAN device  3  causes the access point  2  to which the wireless LAN device  3  is to be connected to be shifted from one to another, the wireless LAN device  3  may keep to use the same IP address, with the result that it is unnecessary to change the setting for network connection in the wireless LAN device  3 . 
     The illustrative embodiment above-described is directed to the wireless LAN system comprised of the wireless mesh network, and description has been made on the exemplary communication protocols, settings and standards. However, the present invention maybe applied without any limitations on the communication protocols, settings and standards so far as the totality of the wireless access devices is adapted to commonly own information for supervising or managing the connection states thereof. 
     In the illustrative embodiment described above, the inter-AP virtual LAN switch  22  has two sorts of tables, MAC address management table  22   b  and inter-AP routing table  22 A. In an application in which the MAC address management table  22 B is adapted to include as the connection access point identification information  113  the name of the access points  2  as shown in  FIG. 3 , however, a table may be provided which is adapted for co-relating the access point names with the IP addresses in order to determine the IP addresses of the access points. That allows the MAC address management table listing the name of the access points to be used at the access point in question to directly specify the IP address of the access points of the destination of transmission. 
     With the illustrative embodiment described above, the access points  2  are configured to have the network side transceiver  21  and the device side transceiver  23  separate from the former. Alternatively, these two transceivers may be integrated with each other, in which case the scale of the access point configuration may be reduced. 
     As described above, the illustrative embodiment is applied to the wireless mesh network effecting wireless transmission between access points. The present invention may also be applied to a telecommunications network entirely or partially implemented by wired connection between the access points. 
     With the illustrative embodiment described above, the use of the data frames  119 ,  135  and  145 ,  FIG. 5 , causes the access point  2  to separate the access point side network from the device side network. However, the access points may be adapted to separate three or more networks from each other. The latter may be accomplished by providing the header field  133  or  147 ,  FIG. 5 , part (B), with additional field of header information on the third network added. 
     With the illustrative embodiment stated above, the functions of the access point  2  are implemented in the form of hardware, only for convenience in description. In practice, these functions may be implemented by software techniques. 
     The entire disclosure of Japanese patent application No. 2004-356899 filed on Dec. 9, 2004, including the specification, claims, accompanying drawings and abstract of the disclosure is incorporated herein by reference in its entirety. 
     While the present invention has been described with reference to the particular illustrative embodiment, it is not to be restricted by the embodiment. It is to be appreciated that those skilled in the art can change or modify the embodiment without departing from the scope and spirit of the present invention.