A software-defined networking (SDN) controller determines multiple paths used for sending a data stream of a specified service from a first network device to a second network device; the SDN controller allocates a path identifier to each path among the multiple paths, the path identifier allocated to each path uniquely corresponding to the path and the specified service; for each path among the multiple paths, the SDN controller delivers forwarding information to a network device expect the second network device on the path, the forwarding information being used for instructing to forward a data stream carrying the path identifier of the path to a next hop of the network device receiving the forwarding information on the path; and the SDN controller selects a path from the multiple paths according to a preset rule, and sends a path identifier of the selected path to the first network device, so that the first network device adds the path identifier of the selected path into the data stream of the specified service.