A control apparatus comprising: monitor means for monitoring statuses of connection of a plurality of communication apparatuses where a synchronous communication is limited to a network in which the control apparatus is arranged, whereby the plurality of communication apparatuses form an asynchronous communication group in a different network; determination means for determining, upon receiving from a first communication apparatus included in the plurality of communication apparatuses a connection request message that requests a connection to the network, whether the first communication apparatus can be connected to the network according to the statuses of the connection of the plurality of communication apparatuses to the network; and communication means for notifying, when it is determined in the determination means that the connection of the first communication apparatus to the network is unavailable, the first communication apparatus of a determination result indicating that the connection is unavailable and a timing at which the connection request message will be transmitted next time, wherein the communication means is configured to transmit, to the first communication apparatus , when it is determined in the determination means that the first communication apparatus , that operates as a representative apparatus among the plurality of communication apparatuses in the network where the synchronous communication is limited, can be connected to the network, a communication timing of the first communication apparatus and a message indicating a communication timing of another communication apparatus included in the plurality of communication apparatuses to cause the first communication apparatus to transmit the message indicating a communication timing of another communication apparatus to the another communication apparatus monitor means for monitoring statuses of connection of a plurality of communication apparatuses where a synchronous communication is limited to a network in which the control apparatus is arranged, whereby the plurality of communication apparatuses form an asynchronous communication group in a different network; determination means for determining, upon receiving from a first communication apparatus included in the plurality of communication apparatuses a connection request message that requests a connection to the network, whether the first communication apparatus can be connected to the network according to the statuses of the connection of the plurality of communication apparatuses to the network; and communication means for notifying, when it is determined in the determination means that the connection of the first communication apparatus to the network is unavailable, the first communication apparatus of a determination result indicating that the connection is unavailable and a timing at which the connection request message will be transmitted next time, wherein the communication means is configured to transmit, to the first communication apparatus , when it is determined in the determination means that the first communication apparatus , that operates as a representative apparatus among the plurality of communication apparatuses in the network where the synchronous communication is limited, can be connected to the network, a communication timing of the first communication apparatus and a message indicating a communication timing of another communication apparatus included in the plurality of communication apparatuses to cause the first communication apparatus to transmit the message indicating a communication timing of another communication apparatus to the another communication apparatus <EOS>