A communication system comprises a transmission apparatus configured to transmit data via a plurality of communication lines, and a reception apparatus configured to receive the data from the transmission apparatus. The transmission apparatus includes processing circuitry configured to generate information regarding QoS of the plurality of communication lines. The processing circuitry is further configured to designate assignment of the data to communication lines of the plurality of communication lines on a basis of at least (i) the information regarding the QoS of the plurality of communication lines and (ii) assignment information indicating an assignment status of a data amount and a communication line transferred in the past. The transmission apparatus includes communication circuitry configured to allocate and transmit the data to the assigned communication lines of the plurality of communication lines on a basis of an instruction from the processing circuitry.