Patent Publication Number: US-2009240834-A1

Title: Management apparatus, communication path control method, communication path control system, and computer-readable storage medium

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to communication performed between communication apparatuses via a relay apparatus. 
     2. Description of the Related Art 
     Wireless LAN (Local Ares Network) products based on the IEEE standards are widely used in recent years. As the connection forms of wireless LAN, an infrastructure mode including a plurality of stations (communication apparatuses) and access points (relay apparatuses), and an ad hoc mode including only a plurality of stations are known. Concerning this technique, a WDS (Wireless Distribution System) using wireless communication between access points and a mesh network formed using a plurality of ad hoc direct communications between stations are also known. Note that the IEEE802.11 standard does not define any detailed relay method for the WDS. 
     A communication path control technique is known, which determines whether traffic to a specific wireless base station has exceeded a threshold. If the traffic is distributable, an instruction for communication path switching is given (Japanese Patent Laid-Open No. 2000-69050). 
     In another known technique, the transmission channel bandwidth is checked before sending a packet to an access point. Then, address information in use of path information is updated based on the check result (Japanese Patent Laid-Open No. 2001-119435). 
     There is known still another technique which inhibits connection of a new station if the number of connected stations is equal to or larger than the maximum connection count, or the communication bandwidth in use of the station is smaller than the minimum communication bandwidth (Japanese Patent Laid-Open No. 2003-101551). 
     Still another known technique determines a communication path based on cost information obtained by calculating a node cost corresponding to the degree of congestion of a wireless base station and a link cost corresponding to the wireless state of a link (Japanese Patent Laid-Open No. 2005-303827). 
     The above-described techniques have various problems. For example, there is not proposed any technique of promoting the efficiency of communication resource utilization by decreasing the number of access points to pass (decreasing the number of communication paths) or the number of frequency channels to be used on the communication paths between the stations via the access points. 
     SUMMARY OF THE INVENTION 
     The present invention enables increasing the speed of communication between communication apparatuses by controlling a communication path which passes through relay apparatuses between the communication apparatuses. 
     According to a first aspect of the present invention, there is provided a management apparatus for managing a plurality of relay apparatuses and a plurality of communication apparatuses which communicate via the relay apparatuses, comprising: a first management unit configured to manage relay apparatus information about communication of each of the relay apparatuses; a second management unit configured to manage connection information about connection between each of the communication apparatuses and a relay apparatus to which the communication apparatus is connected; and a control unit configured to control change of a communication path between the communication apparatuses based on information including the relay apparatus information managed by the first management unit and the connection information managed by the second management unit. 
     According to a second aspect of the present invention, there is provided a communication path control method of a management apparatus for managing a plurality of relay apparatuses and a plurality of communication apparatuses which communicate via the relay apparatuses, comprising: managing relay apparatus information about communication of each of the relay apparatuses; managing connection information about connection between each of the communication apparatuses and a relay apparatus to which the communication apparatus is connected; and controlling change of a communication path between the communication apparatuses based on information including the relay apparatus information and the connection information. 
     According to a third aspect of the present invention, there is provided a communication path control system including a plurality of relay apparatuses, a plurality of communication apparatuses which communicate via the relay apparatuses, and a management apparatus, the management apparatus comprising: a first management unit configured to manage relay apparatus information about communication of each of the relay apparatuses; a second management unit configured to manage connection information about connection between each of the communication apparatuses and a relay apparatus to which the communication apparatus is connected; and a control unit configured to control change of a communication path between the communication apparatuses based on information including the relay apparatus information managed by the first management unit and the connection information managed by the second management unit. 
     According to a fourth aspect of the present invention, there is provided a computer-readable storage medium storing a communication path control program which causes a computer incorporated in a management apparatus for managing a plurality of relay apparatuses and a plurality of communication apparatuses which communicate via the relay apparatuses to function as: a first management unit configured to manage relay apparatus information about communication of each of the relay apparatuses; a second management unit configured to manage connection information about connection between each of the communication apparatuses and a relay apparatus to which the communication apparatus is connected; and a control unit configured to control change of a communication path between the communication apparatuses based on information including the relay apparatus information managed by the first management unit and the connection information managed by the second management unit. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing an example of the overall arrangement of a communication path control system according to an embodiment of the present invention; 
         FIG. 2  is a block diagram showing an example of the functional arrangement of a relay apparatus  20  shown in  FIG. 1 ; 
         FIG. 3  is a block diagram showing an example of the functional arrangement of a communication apparatus  10  shown in  FIG. 1 ; 
         FIG. 4  is a block diagram showing an example of the functional arrangement of a management apparatus  30  shown in  FIG. 1 ; 
         FIG. 5  is a first sequence chart showing an example of the sequence of the operation of communication path control processing in the communication path control system shown in  FIG. 1 ; 
         FIG. 6  is a view showing an example of a relay apparatus information registration message; 
         FIG. 7  is a view showing an example of relay apparatus information; 
         FIG. 8  is a view showing an example of a connection information registration message; 
         FIG. 9  is a view showing an example of connection information; 
         FIG. 10  is a view showing an example of a communication path efficiency promotion request message; 
         FIG. 11  is a view showing an example of a communication path efficiency promotion response message; 
         FIG. 12  is a view showing an example of communication information; 
         FIG. 13  is a second sequence chart showing an example of the sequence of the operation of communication path control processing in the communication path control system shown in  FIG. 1 ; 
         FIG. 14  is a view showing an example of a relay apparatus information registration message; 
         FIG. 15  is a view showing an example of relay apparatus information; 
         FIG. 16  is a view showing an example of a connection information registration message; 
         FIG. 17  is a view showing an example of connection information; 
         FIG. 18  is a view showing an example of a communication path efficiency promotion request message; 
         FIG. 19  is a view showing an example of communication information; 
         FIG. 20  is a third sequence chart showing an example of the sequence of the operation of communication path control processing in the communication path control system shown in  FIG. 1 ; 
         FIG. 21  is a view showing an example of a relay apparatus information registration message; 
         FIG. 22  is a view showing an example of relay apparatus information; 
         FIG. 23  is a view showing an example of a connection information registration message; 
         FIG. 24  is a view showing an example of connection information; 
         FIG. 25  is a view showing an example of a communication path efficiency promotion response message; 
         FIG. 26  is a view showing an example of a connection change instruction message; 
         FIG. 27  is a view showing an example of connection information; 
         FIG. 28  is a fourth sequence chart showing an example of the sequence of the operation of communication path control processing in the communication path control system shown in  FIG. 1 ; 
         FIG. 29  is a view showing an example of a connection change instruction message; 
         FIGS. 30A and 30B  are fifth sequence charts showing an example of the sequence of the operation of communication path control processing in the communication path control system shown in  FIG. 1 ; 
         FIG. 31  is a view showing an example of a communication information registration message; 
         FIG. 32  is a view showing an example of a connection information registration message; 
         FIG. 33  is a view showing an example of a communication path efficiency promotion request message; 
         FIG. 34  is a view showing an example of communication information; 
         FIG. 35  is a view showing an example of connection information; 
         FIGS. 36A and 36B  are sixth sequence charts showing an example of the sequence of the operation of communication path control processing in the communication path control system shown in  FIG. 1 ; 
         FIG. 37  is a view showing an example of a relay apparatus information registration message; 
         FIG. 38  is a view showing an example of relay apparatus information; 
         FIG. 39  is a view showing an example of a connection information registration message; 
         FIG. 40  is a view showing an example of connection information; 
         FIG. 41  is a view showing an example of a communication information registration message; 
         FIG. 42  is a view showing an example of communication information; 
         FIG. 43  is a view showing an example of a connection change instruction message; 
         FIG. 44  is a view showing an example of communication information; 
         FIG. 45  is a view showing an example of connection information; 
         FIG. 46  is a flowchart illustrating the operation of the relay apparatus  20  shown in  FIG. 1 ; 
         FIG. 47  is a flowchart illustrating the operation of the communication apparatus  10  shown in  FIG. 1 ; 
         FIG. 48  is a flowchart illustrating the operation of connection change processing in step S 4708  in  FIG. 47 ; 
         FIG. 49  is a flowchart illustrating the operation of the management apparatus  30  shown in  FIG. 1 ; 
         FIGS. 50A and 50B  are flowcharts illustrating the operation of communication path determination processing in step S 4906  in  FIG. 49 ; 
         FIG. 51  is a flowchart illustrating the operation of first communication path determination processing in step S 5004  in  FIG. 50B ; 
         FIG. 52  is a flowchart illustrating the operation of second communication path determination processing in step S 5009  in  FIG. 50B ; and 
         FIG. 53  is a flowchart illustrating the operation of third communication path determination processing in step S 5011  in  FIG. 50A . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Preferred embodiments of the present invention will now be described in detail with reference to the drawings. It should be noted that the relative arrangement of the components, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. 
     In the following embodiment, an example will be described in which communication paths between communication apparatuses in a wireless LAN network are controlled. However, the present invention is also applicable to a wired network. 
     Embodiment 
       FIG. 1  is a view showing an example of the overall arrangement of a communication path control system according to an embodiment of the present invention. 
     A plurality of communication apparatuses (STA 1  to STA 6 )  10 , a plurality of relay apparatuses (AP 1  to AP 3 )  20 , and a management apparatus  30  are connected to the communication path control system via a wireless LAN network. 
     Each of the communication apparatuses (STA 1  to STA 6 )  10  is connected to one of the relay apparatuses (AP 1  to AP 3 )  20  to form communication paths between the communication apparatuses. The management apparatus  30  manages information to be used to form the communication paths and controls communication path change between the communication apparatuses based on the information. The information managed by the management apparatus  30  includes, for example, information (relay apparatus information) about the relay apparatuses in the network, information (connection information) about connection between the communication apparatuses and the relay apparatuses, and information (communication information) about communication between the communication apparatuses. 
       FIG. 2  is a block diagram showing an example of the functional arrangement of the relay apparatus  20  shown in  FIG. 1 . 
     The relay apparatus  20  includes a CPU (Central Processing Unit)  21 , ROM (Read Only Memory)  22 , RAM (Random Access Memory)  23 , wireless LAN interface  24 , relay apparatus information registration unit  25 , and relay control unit  26 . The CPU  21  comprehensively controls the operation of the relay apparatus  20 . The RAM  23  is used as the work area of the CPU  21 . The ROM  22  stores control programs to be executed by the CPU  21 . The wireless LAN interface  24  provides a wireless LAN communication function. The relay apparatus information registration unit  25  registers, in the management apparatus  30 , relay apparatus information about wireless communication of the relay apparatus. The relay control unit  26  controls the communication relay operation between the communication apparatuses. 
       FIG. 3  is a block diagram showing an example of the functional arrangement of the communication apparatus  10  shown in  FIG. 1 . 
     The communication apparatus  10  includes a CPU  11 , ROM  12 , RAM  13 , wireless LAN interface  14 , connection information registration unit  15 , communication information registration unit  16 , request unit  17 , and communication control unit  18 . The CPU  11  comprehensively controls the operation of the communication apparatus  10 . The RAM  13  is used as the work area of the CPU  11 . The ROM  12  stores control programs to be executed by the CPU  11 . The wireless LAN interface  14  provides a wireless LAN communication function. The connection information registration unit  15  registers, in the management apparatus  30 , connection information about connection between the communication apparatus  10  and a relay apparatus  20 . The communication information registration unit  16  registers, in the management apparatus  30 , communication information about communication between communication apparatuses. The request unit  17  requests the management apparatus  30  to promote the efficiency of the communication paths between the communication apparatuses. The communication control unit  18  controls communication processing of the communication apparatus  10 . 
       FIG. 4  is a block diagram showing an example of the functional arrangement of the management apparatus  30  shown in  FIG. 1 . 
     The management apparatus  30  includes a CPU  31 , ROM  32 , RAM  33 , wireless LAN interface  34 , relay apparatus information management unit  35 , connection information management unit  36 , communication information management unit  37 , communication path determination unit  38 , and communication path control unit  39 . The CPU  31  comprehensively controls the operation of the management apparatus  30 . The RAM  33  is used as the work area of the CPU  31 . The ROM  32  stores control programs (e.g., a communication path control program) to be executed by the CPU  31 . The wireless LAN interface  34  provides a wireless LAN communication function. The relay apparatus information management unit  35  manages relay apparatus information sent from each relay apparatus  20 . The connection information management unit  36  manages connection information sent from each communication apparatus  10 . The communication information management unit  37  manages communication information about communication between the communication apparatuses. Note that the relay apparatus information, connection information, and communication information are stored in, for example, the RAM  33  and managed. The communication path determination unit  38  determines whether to change the communication path between communication apparatuses. The communication path determination unit  38  determines the communication path change based on, for example, the number of relay apparatuses on the communication paths between the communication apparatuses, the number of channels of each relay apparatus, and the frequency bandwidth (to be referred to as a communication bandwidth hereinafter) usable by each relay apparatus. Note that the communication path determination unit  38  also determines whether it is possible to reduce the number of channels used in a relay apparatus  20  on a communication path. The communication path control unit  39  controls the communication path change between communication apparatuses based on the determination result (and also controls to reduce the number of channels used in the relay apparatus  20 ). 
     The functional arrangements of the apparatuses have been described above with reference to  FIGS. 2 to 4 . The functional arrangements can partially or wholly be implemented either by hardware or by causing the CPU to read out and execute programs and data stored in the ROM or the like. 
     The sequence of the operation of communication path control processing in the communication path control system shown in  FIG. 1  will be described with reference to  FIGS. 5 to 45  using several examples. 
       FIG. 5  shows the sequence of processing of causing the communication apparatus (STA 1 )  10  to communicate with the communication apparatus (STA 2 )  10  via the relay apparatus (AP 1 )  20 . An example will be explained in which the communication path does not change. 
     When the processing starts, the relay apparatus (AP 1 )  20  registers information about wireless communication of itself, that is, relay apparatus information in the management apparatus  30 . In the relay apparatus information registration processing, the relay apparatus  20  sends a relay apparatus information registration message to the management apparatus  30  (F 501 ).  FIG. 6  shows an example of the data structure of the relay apparatus information registration message. The relay apparatus information registration message includes a message type, the MAC address of the relay apparatus (relay apparatus identification information), the frequency channel and SSID used in wireless communication of the relay apparatus, and the maximum bandwidth allocatable to wireless communication of the relay apparatus. The relay apparatus information registration message shown in  FIG. 6  sets “relay apparatus information registration” in the message type, “0x000a1b2c3d4e” in the MAC address of the relay apparatus, “1” in the frequency channel, “AP 1 _CH 1 ” in the SSID, and “20 Mbps” in the maximum bandwidth. 
     Upon receiving the relay apparatus information registration message, the management apparatus  30  updates, based on the message, relay apparatus information managed by the relay apparatus information management unit  35 .  FIG. 7  shows an example of relay apparatus information updated based on the relay apparatus information registration message shown in  FIG. 6 . Relay apparatus information includes the MAC address of the relay apparatus, the frequency channel and SSID used in wireless communication of the relay apparatus, and the maximum bandwidth allocatable to wireless communication of the relay apparatus. The relay apparatus information also includes a relay apparatus number to associate a plurality of frequency channels of a relay apparatus. The relay apparatus information need not always include all pieces of information described above, and can include at least one of them. This also applies to other pieces of information. 
     The communication apparatuses (STA 1  and STA 2 ) are connected to the relay apparatus (AP 1 )  20  (F 502  and F 503 ). When connection to the relay apparatus (AP 1 )  20  is done, each of the communication apparatuses (STA 1  and STA 2 ) registers connection information in the management apparatus  30  (F 504  and F 505 ). In the connection information registration processing, each communication apparatus  10  sends a connection information registration message to the management apparatus  30 .  FIG. 8  shows an example of the data structure of the connection information registration message. The connection information registration message includes a message type, the MAC address of the communication apparatus (communication apparatus identification information), the MAC address of the connection destination relay apparatus (connection destination relay apparatus identification information), and the frequency channel used in wireless communication of the relay apparatus.  FIG. 8  shows the connection information registration messages of the communication apparatuses (STA 1  and STA 2 ). More specifically, as the connection information of the communication apparatus (STA 1 )  10 , the message sets “0x0001aabbccdd” in the MAC address of the communication apparatus, “0x000a1b2c3d4e” in the MAC address of the connection destination relay apparatus, and “1” in the frequency channel. As the connection information of the communication apparatus (STA 2 )  10 , the message sets “0x0002bbccddee” in the MAC address of the communication apparatus, “0x000a1b2c3d4e” in the MAC address of the connection destination relay apparatus, and “1” in the frequency channel. Note that “connection information registration” is set in the message type. 
     Upon receiving the connection information registration messages, the management apparatus  30  updates, based on the messages, connection information managed by the connection information management unit  36 .  FIG. 9  shows an example of connection information updated based on the connection information registration messages shown in  FIG. 8 . As shown in  FIG. 9 , connection information includes the MAC address of the communication apparatus, the MAC address of the connection destination relay apparatus, and the frequency channel used in wireless communication of the relay apparatus. 
     The communication apparatus (STA 1 )  10  transmits a communication path efficiency promotion request message (to be also abbreviated as an efficiency promotion request message hereinafter) to the management apparatus  30  prior to the start of data communication with the communication apparatus (STA 2 )  10  (F 506 ).  FIG. 10  shows an example of the data structure of the efficiency promotion request message. The message includes a message type, the MAC address of the communication apparatus, the MAC address of the partner communication apparatus, and the communication bandwidth used in communication. The efficiency promotion request message shown in  FIG. 10  sets “communication path efficiency promotion request” in the message type, “0x0001aabbccdd” in the MAC address of the communication apparatus (STA 1 )  10 , “0x0002bbccddee” in the MAC address of the partner communication apparatus (STA 2 )  10 , and “10 Mbps” in the communication bandwidth. 
     Upon receiving the efficiency promotion request message, the management apparatus  30  executes communication path determination processing, and then transmits a communication path efficiency promotion response message (to be also abbreviated as an efficiency promotion response message hereinafter) to the communication apparatus (STA 1 )  10  of the efficiency promotion request message transmission source (F 507 ).  FIG. 11  shows an example of the data structure of the efficiency promotion response message. The efficiency promotion response message includes a message type and the presence/absence of change of the connection destination relay apparatus. The efficiency promotion response message shown in  FIG. 11  sets “communication path efficiency promotion response” in the message type, and “no connection destination change” in the presence/absence of change of the connection destination relay apparatus. 
     The outline of the communication path determination processing will briefly be described. As is apparent from the connection information described with reference to  FIG. 9 , only one relay apparatus exists on the communication path between the communication apparatuses (STA 1  and STA 2 ). Additionally, only one frequency channel is used between the two communication apparatuses. As for the communication bandwidth, the uplink and downlink of the communication bandwidth (10 Mbps) of the communication apparatus  10  fall within the range of the maximum bandwidth (20 Mbps) of the relay apparatus  20 , as is apparent from the relay apparatus information and the efficiency promotion request message described with reference to  FIGS. 7 and 10 . Hence, in this case, the communication path does not change, and “no change” is set in the connection destination change of the efficiency promotion response message. 
     Upon receiving the communication path efficiency promotion response, the communication apparatus (STA 1 )  10  recognizes that the connection destination relay apparatus does not change, and then starts data communication with the communication apparatus (STA 2 )  10  (F 508 ). 
     After transmitting the efficiency promotion response message, the management apparatus  30  updates communication information managed by the communication information management unit  37 .  FIG. 12  shows an example of the communication information. As shown in  FIG. 12 , the communication information includes the MAC address of the communication apparatus, the MAC address of the partner communication apparatus, and the communication bandwidth to be used. 
       FIG. 13  shows the sequence of processing of causing the communication apparatus (STA 1 )  10  to communicate with the communication apparatus (STA 2 )  10  via the relay apparatus (AP 1 )  20 . An example will be explained in which the communication path does not change. 
     When the processing starts, the relay apparatus (AP 1 )  20  registers relay apparatus information in the management apparatus  30 . In the relay apparatus information registration processing, the relay apparatus  20  sends a relay apparatus information registration message to the management apparatus  30  (F 1301 ).  FIG. 14  shows an example of the data structure of the relay apparatus information registration message.  FIG. 14  shows a relay apparatus information registration message of the relay apparatus  20  having a plurality of frequency channels. The relay apparatus information registration message shown in  FIG. 14  sets “0x000a1b2c3d4e” in the MAC address of the relay apparatus, “1” in the frequency channel, “AP 1 _CH 1 ” in the SSID, and “20 Mbps” in the maximum bandwidth. The message also sets, for another frequency channel, “0x000a1b2c3def” in the MAC address of the relay apparatus, “2” in the frequency channel, “AP 1 _CH 2 ” in the SSID, and “20 Mbps” in the maximum bandwidth. 
     Upon receiving the relay apparatus information registration message, the management apparatus  30  updates, based on the message, relay apparatus information managed by the relay apparatus information management unit  35 .  FIG. 15  shows an example of relay apparatus information updated based on the relay apparatus information registration message shown in  FIG. 14 . In the relay apparatus information shown in  FIG. 15 , since the relay apparatus (AP 1 )  20  has two frequency channels, the same relay apparatus number is assigned to associate the two pieces of information. 
     The communication apparatuses (STA 1  and STA 2 ) are connected to the relay apparatus (AP 1 )  20  (F 1302  and F 1303 ). When connection to the relay apparatus  20  is done, each of the communication apparatuses (STA 1  and STA 2 ) registers connection information in the management apparatus  30  (F 1304  and F 1305 ). In the connection information registration processing, each communication apparatus  10  sends a connection information registration message to the management apparatus  30 .  FIG. 16  shows an example of the data structure of the connection information registration message.  FIG. 16  shows the connection information registration messages of the communication apparatuses (STA 1  and STA 2 ). More specifically, as the connection information of the communication apparatus (STA 1 )  10 , the message sets “0x0001aabbccdd” in the MAC address of the communication apparatus, “0x000a1b2c3d4e” in the MAC address of the connection destination relay apparatus, and “1” in the frequency channel. As the connection information of the communication apparatus (STA 2 )  10 , the message sets “0x0002bbccddee” in the MAC address of the communication apparatus, “0x000a1b2c3def” in the MAC address of the connection destination relay apparatus, and “2” in the frequency channel. 
     Upon receiving the connection information registration messages, the management apparatus  30  updates, based on the messages, connection information managed by the connection information management unit  36 .  FIG. 17  shows an example of connection information updated based on the connection information registration messages shown in  FIG. 16 . As described above, connection information includes the MAC address of the communication apparatus, the MAC address of the connection destination relay apparatus, and the frequency channel used in wireless communication of the relay apparatus. 
     The communication apparatus (STA 1 )  10  transmits an efficiency promotion request message to the management apparatus  30  prior to the start of data communication with the communication apparatus (STA 2 )  10  (F 1306 ).  FIG. 18  shows an example of the data structure of the efficiency promotion request message. The efficiency promotion request message shown in  FIG. 18 , that is, the efficiency promotion request message from the communication apparatus (STA 1 )  10  sets “0x0001aabbccdd” in the MAC address of the communication apparatus (STA 1 )  10 , “0x0002bbccddee” in the MAC address of the partner communication apparatus (STA 2 )  10 , and “15 Mbps” in the communication bandwidth. 
     Upon receiving the efficiency promotion request message, the management apparatus  30  executes communication path determination processing, and then transmits an efficiency promotion response message to the communication apparatus (STA 1 )  10  of the efficiency promotion request message transmission source (F 1307 ). The efficiency promotion response message transmitted here has the same contents as in  FIG. 11  and sets “no connection destination change”. 
     The outline of the communication path determination processing will briefly be described. As is apparent from the relay apparatus information described with reference to  FIG. 15  and the connection information described with reference to  FIG. 17 , only one relay apparatus exists on the communication path between the communication apparatuses (STA 1  and STA 2 ). Additionally, two frequency channels, that is, channel  1  and channel  2  are used between the two communication apparatuses. More specifically, the communication apparatus (STA 1 )  10  communicates with the relay apparatus  20  via channel  1 . The communication apparatus (STA 2 )  10  communicates with the relay apparatus  20  via channel  2 . As for the communication bandwidth, each of the communication bandwidths of channels  1  and  2  falls within the range of the maximum bandwidth (20 Mbps) of the relay apparatus  20 , as is apparent from the relay apparatus information described with reference to  FIG. 15  and the efficiency promotion request message described with reference to  FIG. 18 . Hence, in this case, the communication path does not change, and “no change” is set in the connection destination change of the efficiency promotion response message. 
     Upon receiving the communication path efficiency promotion response, the communication apparatus (STA 1 )  10  recognizes that the connection destination relay apparatus does not change, and then starts data communication with the communication apparatus (STA 2 )  10  (F 1308 ). 
     After transmitting the efficiency promotion response message, the management apparatus  30  updates communication information managed by the communication information management unit  37 .  FIG. 19  shows an example of the communication information. As described above, the communication information includes the MAC address of the communication apparatus, the MAC address of the partner communication apparatus, and the communication bandwidth to be used. 
       FIG. 20  shows the sequence of processing of causing the communication apparatus (STA 1 )  10  to communicate with the communication apparatus (STA 2 )  10  via the relay apparatus (AP 2 )  20 . An example will be explained in which the communication path changes. 
     When the processing starts, the relay apparatus (AP 1 )  20  registers relay apparatus information in the management apparatus  30 . In the relay apparatus information registration processing, the relay apparatus  20  sends a relay apparatus information registration message to the management apparatus  30  (F 2001 ). The relay apparatus information registration message in the process of F 2001  has the same contents as in  FIG. 14 . 
     The relay apparatus (AP 2 )  20  also performs relay apparatus information registration processing (F 2002 ).  FIG. 21  shows an example of the data structure of the relay apparatus information registration message in the process of F 2002 . The relay apparatus information registration message shown in  FIG. 21  sets “0x000b6f7e8d9c” in the MAC address of the relay apparatus, “2” in the frequency channel, “AP 2 _CH 2 ” in the SSID, and “20 Mbps” in the maximum bandwidth. 
     Upon receiving the relay apparatus information registration messages, the management apparatus  30  updates, based on the messages sent from the relay apparatuses (AP 1  and AP 2 ), relay apparatus information managed by the relay apparatus information management unit  35 .  FIG. 22  shows an example of relay apparatus information updated based on the relay apparatus information registration messages shown in  FIGS. 14 and 21 . In the relay apparatus information shown in  FIG. 22 , since the relay apparatus (AP 1 )  20  has two frequency channels, the same relay apparatus number is assigned to associate the channels of the relay apparatus. 
     The communication apparatus (STA 1 )  10  is connected to the relay apparatus (AP 1 )  20  (F 2003 ). The communication apparatus (STA 2 )  10  is connected to the relay apparatus (AP 2 )  20  (F 2004 ). When connection to the relay apparatuses  20  is done, each of the communication apparatuses (STA 1  and STA 2 ) registers connection information in the management apparatus  30  (F 2005  and F 2006 ). In the connection information registration processing, each communication apparatus  10  sends a connection information registration message to the management apparatus  30 .  FIG. 23  shows an example of the data structure of the connection information registration message.  FIG. 23  shows the connection information registration messages of the communication apparatuses (STA 1  and STA 2 ). More specifically, as the connection information of the communication apparatus (STA 1 )  10 , the message sets “0x0001aabbccdd” in the MAC address of the communication apparatus, “0x000a1b2c3d4e” in the MAC address of the connection destination relay apparatus, and “1” in the frequency channel. As the connection information of the communication apparatus (STA 2 )  10 , the message sets “0x0002bbccddee” in the MAC address of the communication apparatus, “0x000b6f7e8d9c” in the MAC address of the connection destination relay apparatus, and “2” in the frequency channel. 
     Upon receiving the connection information registration messages, the management apparatus  30  updates, based on the messages, connection information managed by the connection information management unit  36 .  FIG. 24  shows an example of connection information updated based on the connection information registration messages shown in  FIG. 23 . As described above, connection information includes the MAC address of the communication apparatus, the MAC address of the connection destination relay apparatus, and the frequency channel used in wireless communication of the relay apparatus. 
     The communication apparatus (STA 1 )  10  transmits an efficiency promotion request message to the management apparatus  30  prior to the start of data communication with the communication apparatus (STA 2 )  10  (F 2007 ). The efficiency promotion request message in the process of F 2007  has the same contents as in  FIG. 10 . 
     Upon receiving the efficiency promotion request message, the management apparatus  30  executes communication path determination processing, and then transmits an efficiency promotion response message to the communication apparatus (STA 1 )  10  of the efficiency promotion request message transmission source (F 2008 ).  FIG. 25  shows an example of the data structure of the efficiency promotion response message. The efficiency promotion response message shown in  FIG. 25  sets “connection destination change”. 
     The outline of the communication path determination processing will briefly be described. As is apparent from the relay apparatus information described with reference to  FIG. 22  and the connection information described with reference to  FIG. 24 , two relay apparatuses exist on the communication path between the communication apparatuses (STA 1  and STA 2 ). Additionally, two frequency channels, that is, channel  1  and channel  2  are used between the two communication apparatuses. The communication path is changed to use one relay apparatus between the communication apparatuses (STA 1  and STA 2 ). As for the communication bandwidth, the communication bandwidth between the apparatuses falls within the range of the maximum bandwidth of the relay apparatus  20  regardless of the connection destination which is one of the relay apparatuses (AP 1  and AP 2 ), as is apparent from the relay apparatus information described with reference to  FIG. 22  and the efficiency promotion request message described with reference to  FIG. 10 . Hence, the relay apparatus (AP 2 )  20  having a smaller number of channels is selected as the transit point so that the connection destination relay apparatus of the communication apparatus (STA 1 )  10  of the efficiency promotion request message transmission source changes. For this reason, “change” is set in the connection destination change of the efficiency promotion response message. A relay apparatus having a smaller number of channels is preferentially selected as a transit point because a relay apparatus having a larger number of channels may probably switch the channel more frequently than the relay apparatus having a smaller number of channels. Channel switching often applies a heavy load to the processing of the relay apparatus, resulting in a decrease in the transmission speed. 
     Upon receiving the communication path efficiency promotion response, the communication apparatus (STA 1 )  10  recognizes that the connection destination relay apparatus changes, and receives a connection change instruction message from the management apparatus  30  (F 2009 ).  FIG. 26  shows an example of the data structure of the connection change instruction message. The connection change instruction message includes a message type, the MAC address of the relay apparatus, and the frequency channel and SSID used in wireless communication of the relay apparatus. The connection change instruction message shown in  FIG. 26  sets “connection change instruction” in the message type, “0x000b6f7e8d9c” in the MAC address of the relay apparatus, “2” in the frequency channel, and “AP 2 _CH 2 ” in the SSID. 
     Upon receiving the connection change instruction message, the communication apparatus (STA 1 )  10  is disconnected from the relay apparatus (AP 1 )  20  (F 2010 ) and connected to the relay apparatus (AP 2 )  20  (F 2011 ). The communication apparatus (STA 1 )  10  then starts data communication with the communication apparatus (STA 2 )  10  (F 2012 ). 
     After transmitting the efficiency promotion response message, the management apparatus  30  updates communication information managed by the communication information management unit  37 . The communication information has the same contents as in  FIG. 12 . FIG.  27  shows an example of connection information managed by the connection information management unit  36  of the management apparatus  30  after the above-described communication path change. In the communication information shown in  FIG. 27 , the MAC address of the connection destination relay apparatus has changed from that in the communication information shown in  FIG. 24  before the communication path change. More specifically, the connection destination of the communication apparatus (STA 1 )  10  has changed from the relay apparatus (AP 1 )  20  to the relay apparatus (AP 2 )  20 . 
       FIG. 28  shows the sequence of processing of causing the communication apparatus (STA 1 )  10  to communicate with the communication apparatus (STA 2 )  10  via the relay apparatuses (AP 1  and AP 2 ). An example will be explained in which the communication path changes. 
     When the processing starts, the relay apparatus (AP 1 )  20  registers relay apparatus information in the management apparatus  30 . In the relay apparatus information registration processing, the relay apparatus  20  sends a relay apparatus information registration message to the management apparatus  30  (F 2801 ). The relay apparatus information registration message in the process of F 2801  has the same contents as in  FIG. 14 . 
     The relay apparatus (AP 2 )  20  also performs relay apparatus information registration processing (F 2802 ). The relay apparatus information registration message in the process of F 2802  has the same contents as in  FIG. 21 . 
     Upon receiving the relay apparatus information registration messages, the management apparatus  30  updates, based on the messages sent from the relay apparatuses (AP 1  and AP 2 ), relay apparatus information managed by the relay apparatus information management unit  35 . The relay apparatus information has the same contents as in  FIG. 22 . 
     The communication apparatus (STA 1 )  10  is connected to the relay apparatus (AP 1 )  20  (F 2803 ). The communication apparatus (STA 2 )  10  is connected to the relay apparatus (AP 2 )  20  (F 2804 ). When connection to the relay apparatuses  20  is done, each of the communication apparatuses (STA 1  and STA 2 ) registers connection information in the management apparatus  30  (F 2805  and F 2806 ). In the connection information registration processing, each communication apparatus  10  sends a connection information registration message to the management apparatus  30 . The connection information registration message has the same contents as in  FIG. 23 . Upon receiving the connection information registration messages, the management apparatus  30  updates, based on the messages, connection information managed by the connection information management unit  36 . The connection information has the same contents as in  FIG. 24 . 
     The communication apparatus (STA 1 )  10  transmits an efficiency promotion request message to the management apparatus  30  prior to the start of data communication with the communication apparatus (STA 2 )  10  (F 2807 ). The efficiency promotion request message in the process of F 2807  has the same contents as in  FIG. 18 . 
     Upon receiving the efficiency promotion request message, the management apparatus  30  executes communication path determination processing, and then transmits an efficiency promotion response message to the communication apparatus (STA 1 )  10  of the efficiency promotion request message transmission source (F 2808 ). The efficiency promotion response message transmitted here has the same contents as in  FIG. 11  and sets “no connection destination change”. 
     The outline of the communication path determination processing will briefly be described. As is apparent from the relay apparatus information described with reference to  FIG. 22  and the connection information described with reference to  FIG. 24 , two relay apparatuses exist on the communication path between the communication apparatuses (STA 1  and STA 2 ). Additionally, two frequency channels, that is, channel  1  and channel  2  are used between the two communication apparatuses. The communication path is changed to use one relay apparatus between the communication apparatuses (STA 1  and STA 2 ). As for the communication bandwidth, when the relay apparatus (AP 2 )  20  is selected as the connection destination, the communication bandwidth between the apparatuses exceeds the maximum bandwidth of the relay apparatus  20 , as is apparent from the relay apparatus information described with reference to  FIG. 22  and the efficiency promotion request message described with reference to  FIG. 18 . Hence, the relay apparatus (AP 1 )  20  is selected as the transit point so the connection destination relay apparatus of the communication apparatus (STA 1 )  10  of the efficiency promotion request message transmission source does not change. For this reason, “no change” is set in the connection destination change of the efficiency promotion response message. 
     As the result of the above-described communication path determination processing, the communication path is changed to connect the communication apparatus (STA 2 )  10  to the relay apparatus (AP 1 )  20 . The management apparatus  30  transmits a connection change instruction message to the communication apparatus (STA 2 )  10  (F 2809 ).  FIG. 29  shows an example of the data structure of the connection change instruction message. The connection change instruction message shown in  FIG. 29  sets “connection change instruction” in the message type, “0x000a1b2c3def” in the MAC address of the relay apparatus, “2” in the frequency channel, and “AP 1 _CH 2 ” in the SSID. 
     Upon receiving the connection change instruction message, the communication apparatus (STA 2 )  10  is disconnected from the relay apparatus (AP 2 )  20  (F 2810 ) and connected to the relay apparatus (AP 1 )  20  (F 2811 ). The communication apparatus (STA 2 )  10  then starts data communication with the communication apparatus (STA 1 )  10  (F 2812 ). 
     After transmitting the efficiency promotion response message, the management apparatus  30  updates communication information managed by the communication information management unit  37 . The communication information has the same contents as in  FIG. 19 . Connection information managed by the connection information management unit  36  of the management apparatus  30  after the above-described communication path change is the same as in  FIG. 17 . 
       FIGS. 30A and 30B  show the sequence of processing of causing the communication apparatuses (STA 1  and STA 2 ) to communicate with each other via the relay apparatuses (AP 1  and AP 2 ). In  FIGS. 30A and 30B , the communication apparatuses (STA 3  and STA 4 ) are also connected to the relay apparatus (AP 1 ) to communicate with each other. An example will be explained in which the communication path changes. 
     When the processing starts, the relay apparatus (AP 1 )  20  registers relay apparatus information in the management apparatus  30 . In the relay apparatus information registration processing, the relay apparatus  20  sends a relay apparatus information registration message to the management apparatus  30  (F 3001 ). The relay apparatus information registration message in the process of F 3001  has the same contents as in  FIG. 14 . 
     The relay apparatus (AP 2 )  20  also performs relay apparatus information registration processing (F 3002 ). The relay apparatus information registration message in the process of F 3002  has the same contents as in  FIG. 21 . 
     Upon receiving the relay apparatus information registration messages, the management apparatus  30  updates, based on the messages sent from the relay apparatuses (AP 1  and AP 2 ), relay apparatus information managed by the relay apparatus information management unit  35 . The relay apparatus information has the same contents as in  FIG. 22 . 
     The communication apparatus (STA 1 )  10  is connected to the relay apparatus (AP 1 )  20  (F 3003 ). The communication apparatus (STA 2 )  10  is connected to the relay apparatus (AP 2 )  20  (F 3004 ). When connection to the relay apparatuses  20  is done, each of the communication apparatuses (STA 1  and STA 2 ) registers connection information in the management apparatus  30  (F 3005  and F 3006 ). In the connection information registration processing, each communication apparatus  10  sends a connection information registration message to the management apparatus  30 . The connection information registration message has the same contents as in  FIG. 23 . Upon receiving the connection information registration messages, the management apparatus  30  updates, based on the messages, connection information managed by the connection information management unit  36 . The connection information has the same contents as in  FIG. 24 . 
     After transmitting the connection information registration message, the communication apparatus (STA 1 )  10  transmits not a communication path efficiency promotion request but a communication information registration message to the management apparatus  30  prior to the start of data communication with the communication apparatus (STA 2 )  10  (F 3007 ).  FIG. 31  shows an example of the data structure of the communication information registration message. The communication information registration message includes a message type, the MAC address of the communication apparatus, the MAC address of the partner communication apparatus, and the communication bandwidth used in communication. The communication information registration message shown in  FIG. 31  sets “communication information registration” in the message type, “0x0001aabbccdd” in the MAC address of the communication apparatus (STA 1 )  10 , “0x0002bbccddee” in the MAC address of the partner communication apparatus (STA 2 )  10 , and “10 Mbps” in the communication bandwidth. 
     After communication information registration, the communication apparatus (STA 1 )  10  starts data communication with the communication apparatus (STA 2 )  10  (F 3008 ). Then, the communication apparatuses (STA 3  and STA 4 ) are also connected to the relay apparatus (AP 1 )  20  (F 3009  and F 3010 ). When connection to the relay apparatus  20  is done, each of the communication apparatuses (STA 3  and STA 4 ) registers connection information in the management apparatus  30  (F 3011  and F 3012 ). In the connection information registration processing, each communication apparatus  10  sends a connection information registration message to the management apparatus  30 .  FIG. 32  shows an example of the data structure of the connection information registration message.  FIG. 32  shows the connection information registration messages of the communication apparatuses (STA 3  and STA 4 ). More specifically, as the connection information of the communication apparatus (STA 3 )  10 , the message sets “0x0003ccddeeff” in the MAC address of the communication apparatus, “0x000a1b2c3d4e” in the MAC address of the connection destination relay apparatus, and “1” in the frequency channel. As the connection information of the communication apparatus (STA 4 )  10 , the message sets “0x0004ddeeffaa” in the MAC address of the communication apparatus, “0x000a1b2c3def” in the MAC address of the connection destination relay apparatus, and “2” in the frequency channel. 
     The communication apparatus (STA 3 )  10  transmits an efficiency promotion request message to the management apparatus  30  prior to the start of data communication with the communication apparatus (STA 4 )  10  (F 3013 ).  FIG. 33  shows an example of the data structure of the efficiency promotion request message in the process of F 3013 . The efficiency promotion request message shown in  FIG. 33  sets “0x0003ccddeeff” in the MAC address of the communication apparatus (STA 3 )  10 , “0x0004ddeeffaa” in the MAC address of the partner communication apparatus (STA 4 )  10 , and “15 Mbps” in the communication bandwidth. 
     Upon receiving the efficiency promotion request message, the management apparatus  30  executes communication path determination processing, and then transmits an efficiency promotion response message to the communication apparatus (STA 3 )  10  of the efficiency promotion request message transmission source (F 3014 ). The efficiency promotion response message transmitted here has the same contents as in  FIG. 11  and sets “no connection destination change”. 
     The outline of the communication path determination processing will briefly be described. As is apparent from the relay apparatus information described with reference to  FIG. 22  and the connection information registration message described with reference to  FIG. 32 , only one relay apparatus exists on the communication path between the communication apparatuses (STA 3  and STA 4 ). Hence, the communication path change determination is done for the other communication apparatuses  10  connected to the relay apparatus (AP 1 )  20 . In this case, as is apparent from the relay apparatus information described with reference to  FIG. 22  and the connection information described with reference to  FIG. 24 , two relay apparatuses exist on the communication path between the communication apparatuses (STA 1  and STA 2 ). Additionally, two frequency channels, that is, channel  1  and channel  2  are used between the two communication apparatuses. The communication path is changed to use one relay apparatus on the communication path between the communication apparatuses (STA 1  and STA 2 ) and also use one frequency channel for the communication. As for the communication bandwidth, the communication bandwidth between the apparatuses falls within the range of the maximum bandwidth of the relay apparatus  20  regardless of the connection destination which is one of the relay apparatuses (AP 1  and AP 2 ), as is apparent from the relay apparatus information described with reference to  FIG. 22  and the communication information registration message described with reference to  FIG. 31 . Hence, the relay apparatus (AP 2 )  20  having a smaller number of channels is selected as the transit point so the connection destination relay apparatus of the communication apparatus (STA 3 )  10  of the efficiency promotion request message transmission source does not change. For this reason, “no change” is set in the connection destination change of the efficiency promotion response message. A relay apparatus having a smaller number of channels is preferentially selected as a transit point in order to avoid a decrease in the transmission speed caused by channel switching, as described above. 
     As the result of the communication path determination processing, the communication path is changed to connect the communication apparatus (STA 1 )  10  to the relay apparatus (AP 2 )  20 . The management apparatus  30  transmits a connection change instruction message to the communication apparatus (STA 1 )  10  (F 3015 ). The connection change instruction message has the same contents as in  FIG. 26 . 
     Upon receiving the connection change instruction message, the communication apparatus (STA 1 )  10  is disconnected from the relay apparatus (AP 1 )  20  (F 3016 ) and connected to the relay apparatus (AP 2 )  20  (F 3017 ). The communication apparatus (STA 1 )  10  then resumes data communication with the communication apparatus (STA 2 )  10  (F 3018 ). Data communication between the communication apparatus (STA 3 )  10  and the communication apparatus (STA 4 )  10  starts via the relay apparatus (AP 1 )  20  (F 3019 ). 
     After transmitting the efficiency promotion response message, the management apparatus  30  updates communication information managed by the communication information management unit  37 .  FIG. 34  shows an example of the communication information. As described above, the communication information includes the MAC address of the communication apparatus, the MAC address of the partner communication apparatus, and the communication bandwidth to be used.  FIG. 35  shows an example of connection information managed by the connection information management unit  36  of the management apparatus  30  after the above-described communication path change. As described above, the connection information includes the MAC address of the communication apparatus, the MAC address of the connection destination relay apparatus, and the frequency channel used in wireless communication of the relay apparatus. 
       FIGS. 36A and 36B  show the sequence of processing of causing the communication apparatuses (STA 3  and STA 4 ) to communicate with each other via the relay apparatus (AP 1 )  20  and causing the communication apparatuses (STA 5  and STA 6 ) to communicate with each other via the relay apparatus (AP 2 )  20 . In  FIGS. 36A and 36B , the network arrangement includes the relay apparatus (AP 3 )  20 . An example will be explained in which the communication path changes. 
     When the processing starts, the relay apparatus (AP 1 )  20  registers relay apparatus information in the management apparatus  30 . In the relay apparatus information registration processing, the relay apparatus  20  sends a relay apparatus information registration message to the management apparatus  30  (F 3601 ). The relay apparatus information registration message in the process of F 3601  has the same contents as in  FIG. 14 . 
     The relay apparatuses (AP 2  and AP 3 )  20  also perform relay apparatus information registration processing (F 3602  and F 3603 ). The relay apparatus information registration message in the process of F 3602  has the same contents as in  FIG. 21 .  FIG. 37  shows an example of the data structure of the relay apparatus information registration message in the process of F 3603 . The relay apparatus information registration message shown in  FIG. 37  sets “0x000c3d4e5f6a” in the MAC address of the relay apparatus, “3” in the frequency channel, “AP 3 _CH 3 ” in the SSID, and “20 Mbps” in the maximum bandwidth. 
     Upon receiving the relay apparatus information registration messages, the management apparatus  30  updates relay apparatus information managed by the relay apparatus information management unit  35 .  FIG. 38  shows an example of relay apparatus information. As described above, relay apparatus information includes the MAC address of the relay apparatus, the frequency channel and SSID used in wireless communication of the relay apparatus, and the maximum bandwidth allocatable to wireless communication of the relay apparatus. The relay apparatus information also includes a relay apparatus number to associate a plurality of frequency channels of a relay apparatus. 
     The communication apparatus (STA 1 )  10  is connected to the relay apparatus (AP 1 )  20  (F 3604 ). The communication apparatus (STA 2 )  10  is connected to the relay apparatus (AP 2 )  20  (F 3605 ). The communication apparatuses (STA 3  and STA 4 ) are connected to the relay apparatus (AP 1 )  20  (F 3606 ). The communication apparatuses (STA 5  and STA 6 ) are connected to the relay apparatus (AP 2 )  20  (F 3607 ). 
     When connection to the relay apparatuses is done, each of the communication apparatuses (STA 1  to STA 6 ) registers connection information in the management apparatus  30  (F 3608 , F 3609 , F 3610 , and F 3611 ). In the connection information registration processing, each communication apparatus  10  sends a connection information registration message to the management apparatus  30 .  FIG. 39  shows an example of the data structure of the connection information registration message in each of the communication apparatuses (STA 1  to STA 6 ). Referring to  FIG. 39 , as the connection information of the communication apparatus (STA 1 )  10 , the message sets “0x0001aabbccdd” in the MAC address of the communication apparatus, “0x000a1b2c3d4e” in the MAC address of the connection destination relay apparatus, and “1” in the frequency channel. As the connection information of the communication apparatus (STA 2 )  10 , the message sets “0x0002bbccddee” in the MAC address of the communication apparatus, “0x000b6f7e8d9c” in the MAC address of the connection destination relay apparatus, and “2” in the frequency channel. As the connection information of the communication apparatus (STA 3 )  10 , the message sets “0x0003ccddeeff” in the MAC address of the communication apparatus, “0x000a1b2c3d4e” in the MAC address of the connection destination relay apparatus, and “1” in the frequency channel. As the connection information of the communication apparatus (STA 4 )  10 , the message sets “0x0004ddeeffaa” in the MAC address of the communication apparatus, “0x000a1b2c3d4e” in the MAC address of the connection destination relay apparatus, and “1” in the frequency channel. As the connection information of the communication apparatus (STA 5 )  10 , the message sets “0x0005eeffaabb” in the MAC address of the communication apparatus, “0x000b6f7e8d9c” in the MAC address of the connection destination relay apparatus, and “2” in the frequency channel. As the connection information of the communication apparatus (STA 6 )  10 , the message sets “0x0006ffaabbcc” in the MAC address of the communication apparatus, “0x000b6f7e8d9c” in the MAC address of the connection destination relay apparatus, and “2” in the frequency channel. 
     Upon receiving the connection information registration messages, the management apparatus  30  updates, based on the messages, connection information managed by the connection information management unit  36 .  FIG. 40  shows an example of connection information updated based on the connection information registration messages shown in  FIG. 39 . As described above, connection information includes the MAC address of the communication apparatus, the MAC address of the connection destination relay apparatus, and the frequency channel used in wireless communication of the relay apparatus. 
     Next, the communication apparatus (STA 3 )  10  transmits not a communication path efficiency promotion request but a communication information registration message to the management apparatus  30  prior to the start of data communication with the communication apparatus (STA 4 )  10  (F 3612 ) The communication apparatus (STA 5 )  10  also transmits not a communication path efficiency promotion request but a communication information registration message to the management apparatus  30  prior to the start of data communication with the communication apparatus (STA 6 )  10  (F 3613 ).  FIG. 41  shows an example of the data structure of the communication information registration messages in the processes of F 3612  and F 3613 .  FIG. 41  shows the communication information registration messages of the communication apparatuses (STA 3  and STA 5 ). More specifically, the communication information registration message transmitted from the communication apparatus (STA 3 )  10  sets “0x0003ccddeeff” in the MAC address of the communication apparatus (STA 3 )  10 , “0x0004ddeeffaa” in the MAC address of the partner communication apparatus (STA 4 )  10 , and “10 Mbps” in the communication bandwidth. The communication information registration message transmitted from the communication apparatus (STA 5 )  10  sets “0x0005eeffaabb” in the MAC address of the communication apparatus (STA 5 )  10 , “0x0006ffaabbcc” in the MAC address of the partner communication apparatus (STA 6 )  10 , and “10 Mbps” in the communication bandwidth. 
     After communication information registration, the communication apparatuses (STA 3  and STA 4 ) start data communication (F 3614 ). The communication apparatuses (STA 5  and STA 6 ) also start data communication (F 3615 ).  FIG. 42  shows an example of communication information managed by the communication information management unit  37  of the management apparatus  30 . As described above, communication information includes the MAC address of the communication apparatus, the MAC address of the partner communication apparatus, and the communication bandwidth to be used. 
     The communication apparatus (STA 1 )  10  transmits an efficiency promotion request message to the management apparatus  30  (F 3616 ). The efficiency promotion request message in the process of F 3616  has the same contents as in  FIG. 10 . 
     Upon receiving the efficiency promotion request message, the management apparatus  30  executes communication path determination processing, and then transmits an efficiency promotion response message to the communication apparatus (STA 1 )  10  of the efficiency promotion request message transmission source (F 3617 ). The efficiency promotion response message transmitted here has the same contents as in  FIG. 25  and sets “connection destination change”. 
     The outline of the communication path determination processing will briefly be described. As is apparent from the relay apparatus information described with reference to  FIG. 38  and the connection information described with reference to  FIG. 40 , two relay apparatuses exist on the communication path between the communication apparatuses (STA 1  and STA 2 ). Additionally, two frequency channels, that is, channel  1  and channel  2  are used between the two communication apparatuses. The communication path is changed to use one relay apparatus on the communication path between the communication apparatuses (STA 1  and STA 2 ) and also use one frequency channel for the communication. The relay apparatuses (AP 1  and AP 2 )  20  serving as transit points between the communication apparatuses (STA 1  and STA 2 ) are compared. The number of channels is smaller in the relay apparatus (AP 2 )  20 . Hence, the relay apparatus (AP 2 )  20  is selected as a connection destination candidate. However, the relay apparatus (AP 2 )  20  is used for the communication between the communication apparatuses (STA 5  and STA 6 ) and has no extra communication bandwidth (a free bandwidth of a predetermined range or more). Hence, the relay apparatus (AP 3 )  20  having an extra communication bandwidth is selected as the transit point so that the connection destination relay apparatus of the communication apparatus (STA 1 )  10  of the efficiency promotion request message transmission source changes. For this reason, “change” is set in the connection destination change of the efficiency promotion response message. 
     After transmitting the efficiency promotion response message, the management apparatus  30  transmits a connection change instruction message to the communication apparatuses (STA 1  and STA 2 ) (F 3618  and F 3619 ).  FIG. 43  shows an example of the data structure of the connection change instruction message. The connection change instruction message shown in  FIG. 43  sets “connection change instruction” in the message type, “0x000c3d4e5f6a” in the MAC address of the relay apparatus, “3” in the frequency channel, and “AP 3 _CH 3 ” in the SSID. 
     Upon receiving the connection change instruction message, the communication apparatus (STA 1 )  10  is disconnected from the relay apparatus (AP 1 )  20  (F 3620 ) and connected to the relay apparatus (AP 3 )  20  (F 3621 ). Similarly, upon receiving the connection change instruction message, the communication apparatus (STA 2 )  10  is disconnected from the relay apparatus (AP 2 )  20  (F 3622 ) and connected to the relay apparatus (AP 3 )  20  (F 3623 ). The communication apparatuses (STA 1  and STA 2 ) then start data communication (F 3624 ). 
     After transmitting the efficiency promotion response message, the management apparatus  30  updates communication information managed by the communication information management unit  37 .  FIG. 44  shows an example of the communication information. As described above, the communication information includes the MAC address of the communication apparatus, the MAC address of the partner communication apparatus, and the communication bandwidth to be used.  FIG. 45  shows an example of connection information managed by the connection information management unit  36  of the management apparatus  30  after the above-described communication path change. 
     The sequence of the operation of each apparatus in the communication path control system shown in  FIG. 1  will be described next with reference to the flowcharts in  FIGS. 46 to 53 . 
     The operation of the relay apparatus  20  will be described with reference to  FIG. 46 . 
     When the processing starts, the relay apparatus  20  executes relay apparatus information registration processing. In this processing, the relay apparatus information registration unit  25  transmits a relay apparatus information registration message to the management apparatus  30 , thereby registering, in the management apparatus  30 , information about wireless communication of the relay apparatus  20  (S 4601 ). 
     When the communication apparatuses  10  are connected, the relay apparatus  20  causes the relay control unit  26  to perform a relay operation between the communication apparatuses (S 4602 ). Then, the relay apparatus  20  determines whether to end the relay operation. This determination is done continuously during the relay operation (NO in step S 4603 ). To end the relay operation (YES in step S 4603 ), the relay apparatus  20  causes the relay apparatus information registration unit  25  to request the management apparatus  30  to delete the relay apparatus information registered in the process of step S 4601  (S 4604 ), and ends the relay operation. 
     The operation of the communication apparatus  10  will be described next with reference to  FIG. 47 . 
     When the processing starts, the communication apparatus  10  is connected to the relay apparatus  20  to communicate with the management apparatus  30  or another communication apparatus  10  (S 4701 ). The communication apparatus  10  causes the connection information registration unit  15  to transmit a connection information registration message to the management apparatus  30 , thereby registering, in the management apparatus  30 , information about wireless communication with the relay apparatus  20  connected in the process of step S 4701  (S 4702 ). 
     After that, the communication apparatus  10  determines whether to start communication with the communication partner apparatus. If communication is not to be started (NO in step S 4703 ), the process advances to step S 4711 . To start communication with the communication partner apparatus (YES in step S 4703 ), the communication apparatus  10  causes the communication control unit  18  to determine whether to request communication path efficiency promotion of the management apparatus  30 . If whether to request efficiency promotion is set by, for example, the apparatus settings, the efficiency promotion request is executed based on the information. Alternatively, the request may be executed upon detecting that the transmission speed has reduced to a predetermined value or less. 
     If the efficiency promotion request is not to be output (NO in step S 4704 ), the communication apparatus  10  causes the communication information registration unit  16  to transmit a communication information registration message to the management apparatus  30 , thereby registering, in the management apparatus  30 , information about communication between the communication apparatuses (S 4709 ). Then, the communication apparatus  10  starts data communication (S 4710 ). 
     On the other hand, to request communication path efficiency promotion (YES in step S 4704 ), the communication apparatus  10  causes the request unit  17  to transmit an efficiency promotion request message to the management apparatus  30  (S 4705 ). Upon receiving an efficiency promotion response message corresponding to the request (S 4706 ), the communication apparatus  10  causes the communication control unit  18  to determine, by referring to the message, whether the communication path should be changed. If the communication path should not be changed (NO in step S 4707 ), the communication apparatus  10  starts data communication (S 4710 ). If the communication path should be changed (YES in step S 4707 ), the communication apparatus  10  executes connection change processing (to be described later in detail) to change the connection destination relay apparatus (S 4708 ). Then, the communication apparatus  10  starts data communication (S 4710 ). 
     To perform another operation after the data communication (NO in step S 4711 ), the communication apparatus  10  returns to the process in step S 4703 . Note that the communication apparatus  10  requests the management apparatus  30  to delete the communication information at the end of data communication. 
     Upon determining in step S 4711  to end the operation (YES in step S 4711 ), the communication apparatus  10  causes the communication control unit  18  to disconnect the relay apparatus  20  (S 4712 ). The communication apparatus  10  causes the connection information registration unit  15  to request the management apparatus  30  to delete the connection information registered in the process of step S 4701  (S 4713 ), and ends the processing. 
     Details of the operation of the connection change processing in step S 4708  of  FIG. 47  will be described with reference to  FIG. 48 . 
     When the connection change processing starts, the communication apparatus  10  causes the communication control unit  18  to determine whether a connection change instruction message is received from the management apparatus  30 . If no connection change instruction message is received (NO in step S 4801 ), the processing directly ends. If a connection change instruction message is received (YES in step S 4801 ), the communication apparatus  10  causes the communication control unit  18  to determine whether connection to the relay apparatus  20  designated in the connection change instruction message is possible. This determination is done in, for example, a wireless LAN environment based on whether the communication apparatus can receive beacons from the relay apparatus  20  designated in the connection change instruction message. 
     If it is determined that connection to the designated relay apparatus  20  is impossible (NO in step S 4802 ), the communication apparatus  10  causes the communication control unit  18  to transmit a message representing the connection change disable state to the management apparatus  30  (S 4805 ), and ends the processing. If connection to the designated relay apparatus  20  is possible (YES in step S 4802 ), the communication apparatus  10  disconnects the relay apparatus  20  that is currently being connected (S 4803 ). The communication apparatus  10  changes the connection to the relay apparatus  20  designated in the connection change instruction message (S 4804 ), and ends the processing. 
     The operation of the management apparatus  30  will be described next with reference to  FIG. 49 . 
     When the processing starts, the management apparatus  30  determines whether a relay apparatus information registration or deletion request is received from the relay apparatus  20 . Upon receiving a relay apparatus information registration or deletion request (YES in step S 4901 ), the management apparatus  30  updates, based on the request, relay apparatus information managed by the relay apparatus information management unit  35  (S 4902 ), and the process advances to step S 4903 . 
     If no relay apparatus information registration or deletion request is received (NO in step S 4901 ), the management apparatus  30  determines whether a connection information registration or deletion request is received from the communication apparatus  10 . Upon receiving a connection information registration or deletion request (YES in step S 4903 ), the management apparatus  30  updates, based on the request, connection information managed by the connection information management unit  36  (S 4904 ), and the process advances to step S 4905 . 
     If no connection information registration or deletion request is received (NO in step S 4903 ), the management apparatus  30  determines whether a communication path efficiency promotion request is received from the communication apparatus  10 . If no communication path efficiency promotion request is received (NO in step S 4905 ), the management apparatus  30  determines whether a communication information registration or deletion request is received from the communication apparatus  10 . If no communication information registration or deletion request is received (NO in step S 4910 ), the management apparatus  30  returns to the process in step S 4901 . On the other hand, upon receiving a communication information registration or deletion request (YES in step S 4910 ), the management apparatus  30  updates communication information managed by the communication information management unit  37  (S 4911 ), and returns to the process in step S 4901 . 
     Upon receiving a communication path efficiency promotion request from the communication apparatus  10  in step S 4905  (YES in step S 4905 ), the management apparatus  30  causes the communication path determination unit  38  to execute communication path determination processing (to be described later in detail) (S 4906 ). If the connection destination relay apparatus of the communication apparatus should not be changed as the result of processing (NO in step S 4907 ), the management apparatus  30  updates communication information managed by the communication information management unit  37  (S 4911 ), and returns to the process in step S 4901 . If the connection destination relay apparatus of the communication apparatus  10  should be changed (YES in step S 4907 ), the management apparatus  30  causes the communication path control unit  39  to control the communication path based on the result of the communication path determination processing. More specifically, the management apparatus  30  transmits a connection change instruction message to the communication apparatus  10  which requires a connection destination change (S 4908 ). 
     After transmitting the message, the management apparatus  30  updates the connection information managed by the connection information management unit  36  and the communication information managed by the communication information management unit  37  (S 4909 ). Note that upon receiving a connection change disable message from the communication apparatus  10 , the management apparatus  30  does not change the connection information about the communication apparatus of the message transmission source. 
     Then, the management apparatus  30  determines whether to end its operation. To end the operation (YES in step S 4912 ), the management apparatus  30  directly ends the processing. To continue the operation (NO in step S 4912 ), the management apparatus  30  returns to the process in step S 4901 . 
     Details of the operation of the communication path determination processing in step S 4906  of  FIG. 49  will be described with reference to  FIGS. 50A and 50B . 
     When the processing starts, the management apparatus  30  determines whether a predetermined number (e.g., two) or more of relay apparatuses exist between the communication apparatus of the efficiency promotion request message transmission source and the communication partner apparatus designated by the request. If the number of relay apparatuses is smaller than the predetermined number (NO in step S 5001 ), the management apparatus  30  transmits an efficiency promotion response message (no connection destination change) to the communication apparatus  10  of the efficiency promotion request message transmission source (S 5010 ). After that the management apparatus  30  executes third communication path determination processing (S 5011 ), and ends the processing. 
     Upon determining in step S 5001  that a predetermined number or more of relay apparatuses exist (YES in step S 5001 ), the management apparatus  30  determines whether the relay apparatuses  20  on the communication path include a relay apparatus having a predetermined number (e.g., one) or less of channels. This determination is performed to prefer, as a transit point, a relay apparatus having a smaller number of channels to one having a larger number of channels and avoid a decrease in the transmission speed caused by channel switching, as described above. 
     Upon determining that there is no relay apparatus  20  having the predetermined number or less of channels (NO in step S 5002 ), the management apparatus  30  executes second communication path determination processing (S 5009 ), and ends the processing. 
     Upon determining in step S 5002  that there is the relay apparatus  20  having the predetermined number or less of channels (YES in step S 5002 ), the management apparatus  30  determines whether the relay apparatus  20  having the predetermined number or less of channels has a free bandwidth of a predetermined range or more. Whether the relay apparatus has a free bandwidth of a predetermined range or more is determined based on, for example, a threshold defined in advance. If a free bandwidth of a predetermined range or more exists (YES in step S 5003 ), the management apparatus  30  executes first communication path determination processing (S 5004 ), and ends the processing. If no free bandwidth of a predetermined range or more exists (NO in step S 5003 ), the management apparatus  30  determines whether there is another relay apparatus that is not located on the communication path between the communication apparatus of the efficiency promotion request message transmission source and the communication partner apparatus designated by the request. This relay apparatus will be referred to as a third relay apparatus hereinafter. If no third relay apparatus exists (NO in step S 5005 ), the management apparatus  30  executes second communication path determination processing (S 5009 ), and ends the processing. 
     Upon determining in step S 5005  that there is a third relay apparatus (YES in step S 5005 ), the management apparatus  30  determines whether the relay apparatus has a free bandwidth of a predetermined range or more. If no free bandwidth of a predetermined range or more exists (NO in step S 5006 ), the management apparatus  30  executes second communication path determination processing (S 5009 ), and ends the processing. If a free bandwidth of a predetermined range or more exists (YES in step S 5006 ), the management apparatus  30  transmits an efficiency promotion response message (connection destination change) to the efficiency promotion request message transmission source apparatus (S 5007 ). After that, the management apparatus  30  causes the communication path determination unit  38  to return a determination result “connection between the efficiency promotion request message transmission source apparatus and the communication partner apparatus designated by the request should be changed to the third relay apparatus” (S 5008 ), and ends the processing. 
     Details of the operation of the first communication path determination processing in step S 5004  of  FIG. 50B  will be described next with reference to  FIG. 51 . In this processing, the connection destination relay apparatus of the communication apparatus  10  changes to a relay apparatus having a predetermined number or less of channels. 
     When the processing starts, the management apparatus  30  determines whether the communication apparatus of the efficiency promotion request message transmission source is connected to the relay apparatus  20  having a predetermined number (e.g., one) or less of channels. If the communication apparatus is connected to the relay apparatus  20  having the predetermined number or less of channels (YES in step S 5101 ), the management apparatus  30  transmits an efficiency promotion response message (no connection destination change) to the message transmission source apparatus (S 5102 ). The management apparatus  30  causes the communication path determination unit  38  to return a determination result “the relay apparatus to which the communication partner apparatus designated by the efficiency promotion request message is connected should be changed to the relay apparatus connected to the message transmission source apparatus” (S 5103 ). The management apparatus  30  then ends the processing. 
     If the efficiency promotion request message transmission source apparatus is not connected to the relay apparatus having the predetermined number or less of channels (NO in step S 5101 ), the management apparatus  30  transmits an efficiency promotion response message to the message transmission source apparatus (S 5104 ). Note that “connection destination change” is set in the efficiency promotion response message. The management apparatus  30  causes the communication path determination unit  38  to return a determination result “the relay apparatus to which the communication apparatus of the efficiency promotion request message transmission source is connected should be changed to the relay apparatus connected to the communication partner apparatus designated by the message” (S 5105 ). The management apparatus  30  then ends the processing. 
     Details of the operation of the second communication path determination processing in step S 5009  of  FIG. 50B  will be described next with reference to  FIG. 52 . In this processing, the connection destination relay apparatus of the communication apparatus  10  changes to a relay apparatus having channels more than a predetermined number. 
     When the processing starts, the management apparatus  30  determines whether the communication apparatus of the efficiency promotion request message transmission source is connected to the relay apparatus  20  having a predetermined number (e.g., one) or less of channels. If the communication apparatus is connected to the relay apparatus  20  having the predetermined number or less of channels (YES in step S 5201 ), the management apparatus  30  transmits a communication path efficiency promotion response message (connection destination change) to the message transmission source apparatus (S 5202 ). The management apparatus  30  causes the communication path determination unit  38  to return a determination result “the relay apparatus to which the communication apparatus of the efficiency promotion request message transmission source is connected should be changed to the relay apparatus connected to the communication partner apparatus designated by the message” (S 5203 ). The management apparatus  30  then ends the processing. 
     If the efficiency promotion request message transmission source apparatus is not connected to the relay apparatus having the predetermined number or less of channels (NO in step S 5201 ), the management apparatus  30  transmits an efficiency promotion response message (no connection destination change) to the message transmission source apparatus (S 5204 ). The management apparatus  30  causes the communication path determination unit  38  to return a determination result “the relay apparatus to which the communication partner apparatus designated by the efficiency promotion request message is connected should be changed to the relay apparatus connected to the message transmission source apparatus” (S 5205 ). The management apparatus  30  then ends the processing. 
     Details of the operation of the third communication path determination processing in step S 5011  of  FIG. 50A  will be described next with reference to  FIG. 53 . 
     When the processing starts, the management apparatus  30  determines whether another communication apparatus which communicates with the communication apparatus of the message transmission source via a predetermined number or more of relay apparatuses is connected to the relay apparatus to which the communication apparatus of the message transmission source is connected. 
     If no such a communication apparatus exists (NO in step S 5301 ), the management apparatus  30  causes the communication path determination unit  38  to return a determination result “the communication path should not be changed” (S 5304 ), and ends the processing. If such a communication apparatus exists (YES in step S 5301 ), the management apparatus  30  determines whether the relay apparatuses  20  to which the communication apparatus is connected include a relay apparatus  20  having a free bandwidth of a predetermined range or more. If no relay apparatus  20  having a free bandwidth of a predetermined range or more exists (NO in step S 5302 ), the management apparatus  30  causes the communication path determination unit  38  to return a determination result “the communication path should not be changed” (S 5304 ), and ends the processing. If the relay apparatus  20  having a free bandwidth of a predetermined range or more exists (YES in step S 5302 ), the management apparatus  30  causes the communication path determination unit  38  to return a determination result “the connection destination of the communication apparatus should be changed to the relay apparatus having a free bandwidth of a predetermined range or more” (S 5303 ), and ends the processing. 
     The above description of  FIGS. 50A and 50B  to  53  has not mentioned any processing of decreasing the number of channels used by the relay apparatus  20 . However, this processing is executed as needed when changing the communication path, as described with reference to  FIGS. 5 to 45 . 
     An example of the typical embodiment of the present invention has been described above. The present invention is not limited to the above-described embodiment shown in the drawings, and changes and modifications can be made as needed without departing from the spirit and scope of the present invention. 
     For example, in the description of  FIG. 50A , communication path control is done by determining the number of relay apparatuses (S 5001 ), the number of channels of each relay apparatus (S 5002 ), and the communication bandwidth of each relay apparatus (S 5003 ). The order of determinations may be changed. Instead of performing all determinations, one of them may selectively be performed. 
     In the above description, a relay apparatus having a smaller number of channels is preferentially selected as a transit point. This aims at avoiding a decrease in the transmission speed caused by channel switching, as described above. Any other information may be determined if a relay apparatus with less or no channel switching is selectable. 
     The present invention can take a form of, for example, a system, apparatus, method, program, or storage medium. More specifically, the present invention is applicable to a system including a plurality of devices, or an apparatus including a single device. 
     The present invention also incorporates a case in which the functions of the above-described embodiment are achieved by supplying a software program to the system or apparatus directly or from a remote site and causing the computer of the system or apparatus to read out and execute the supplied program code. In this case, the supplied program is a computer program corresponding to the flowcharts illustrated in the embodiment. 
     Hence, the program code itself, which is installed in the computer to implement the functional processing of the present invention by the computer, also implements the present invention. That is, the present invention incorporates the computer program itself for implementing the functional processing of the present invention. In this case, the program can take any form such as an object code, a program to be executed by an interpreter, or script data to be supplied to the OS (Operating System) as long as the functions of the program can be obtained. 
     Examples of the computer-readable storage medium to supply the computer program are a floppy® disk, hard disk, optical disk, magnetooptical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, and DVD (DVD-ROM or DVD-R). 
     As another program supply method, a client computer may be connected to a homepage on the Internet by using a browser to download the computer program of the present invention from the homepage to a recording medium such as a hard disk. In this case, the program to be downloaded may be a compressed file containing an automatic installation function. The program code contained in the program of the present invention may be divided into a plurality of files, and the files may be downloaded from different homepages. That is, the present invention also incorporates a WWW server which causes a plurality of users to download a program file that implements the functional processing of the present invention by a computer. 
     The program of the present invention may be encrypted, stored in a storage medium such as a CD-ROM, and delivered to users. Any user who satisfies predetermined conditions may be allowed to download key information for decryption from a homepage via the Internet so that he/she can execute the encrypted program by using the key information and install the program in the computer. 
     The functions of the above-described embodiment can be implemented not only when the computer executes the readout program but also in cooperation with, for example, the OS running on the computer based on the instructions of the program. In this case, the OS or the like partially or wholly executes actual processing, thereby implementing the functions of the above-described embodiment. 
     Alternatively, some or all of the functions of the above-described embodiment may be implemented by writing the program read out from the recording medium in the memory of a function expansion board inserted into the computer or a function expansion unit connected to the computer. In this case, after the program is written in the function expansion board or function expansion unit, the CPU of the function expansion board or function expansion unit partially or wholly executes actual processing based on the instructions of the program. 
     According to the present invention, since load on a relay apparatus is reduced by controlling the communication path between communication apparatuses via the relay apparatus, it is possible to increase the speed of communication between the communication apparatuses. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2008-070052, filed Mar. 18, 2008, which is hereby incorporated by reference herein in its entirety.