The method includes: receiving, by a first device, a first packet from a second device, where the first packet includes a primary scheduling identifier, and the primary scheduling identifier is used to identify that the second device has permission to select a path; determining, by the first device, a first path used to transmit the first packet; sending, by the first device, a second packet to the second device by using the first path, where the second packet includes a following identifier, and the following identifier is used to identify that the first device sends the packet by using a transmission path selected by a device other than the first device. This can ensure that a same path is used for bidirectional packet transmission between two communication parties while ensuring service quality, in a complex SD-WAN path selection scenario.