A method includes receiving, by a first device, a data packet that includes a first time information indicating a time at which the data packet arrives at a first wireless protocol layer of a second device. The first wireless protocol layer is located in a user plane protocol stack of the second device. A header of the data packet is a header of the first wireless protocol layer. The method further includes determining, by the first device, a second time information and a transmission delay of the data packet between the second device and the first device based on the first and second time information. The second time information indicates a time at which the data packet leaves a second wireless protocol layer located in a user plane protocol stack of the first device. The header of the data packet is parsed at the second wireless protocol layer.