Embodiments of the present invention provide a data transmission method, a transmission control method, and a device. An SDN includes: a network controller, a first edge node, and at least one second edge node, where the network controller provides a target routing rule for the first edge node, the first edge node receives a data packet that needs to be transmitted, determines a target edge node, acquires the target routing rule from the network controller according to the target edge node, and sends the data packet to the target edge node according to the target routing rule; and when used as the target edge node, the at least one second edge node receives the data packet sent by the first edge node, and complete transmission of the data packet. The technical solutions in the present invention can improve communication efficiency of the SDN.