A system and method for controlling the transmission of contents among a plurality of audio/video (AV) devices by using a general purpose network In case of transmitting the contents held in a first device (source) to a second device (sink) by way of a designated transmission path, information relating to the transfer protocol for transmitting the contents is added to each content when the contents information held in the first device is disclosed to a controller on the network. Transmission management is performed based on the information on the transfer protocol added to each content when starting transmission of the contents between the first device and the second device.