An embodiment method includes: a first service atom receives a second packet sent by a central switching device, where a first service packet is encapsulated in the second packet and the second packet further includes a first service path identifier. The first service atom performs first service processing according to information in the first service packet, to obtain a first processing result. The first service atom queries a first path switching entry according to the first processing result and the first service path identifier. The first service atom sends a third packet to the central switching device, where a source device identifier of the third packet is a device identifier of the first service atom, a second service packet is encapsulated in the third packet, and the third packet includes the second service path identifier.