Embodiments provide an SDN, an SDN configuration method, an SDN-based data transmission method, and a network controller. A data packet combination function and a data packet split function are separately configured on nodes in the SDN. Therefore, when data packets of a first service are received, multiple small data packets of the first service may be combined into one large data packet. In comparison with transmission of the multiple small data packets, transmission efficiency of the SDN can be improved by transmitting the combined data packet.