A router of a first network and a router of a second network are connected to a third network. A connection request including information relating to the direction of communication performed by a first service provider that exists on the first network is transmitted from the first network to the second network via the third network. On the basis of the information relating to the direction of communication included in the connection request transmitted from the first network to the second network, a second service provider that exists on the second network is selected and a response that includes identification information of the selected second service provider is transmitted from the second network to the first network via the third network.