Embodiments of the present disclosure provide a method. According to the method, a mark is added to a data packet. After user equipment is handed over from an original device to a target device, and before a user plane network element receives a handover notification, the user plane network element sends, through a path used before handover, a data packet that carries a first mark to the original device. The original device modifies the first mark in the data packet to a second mark, and then forwards, to the target device, a data packet whose mark is modified and that carries the second mark. After receiving the handover notification, the user plane network element sends, to the target device, a data packet that carries a fourth mark. The target device can distinguish between sources of the received data packets based on different marks in the received data packets.