A first communication apparatus obtains a sampling cycle. The sampling cycle is a time interval at which the first communication apparatus samples occupancy of a first buffer. The first buffer is used to store a data packet of a first priority. The first communication apparatus determines occupancy of the first buffer at a first sampling moment based on the sampling cycle. The first communication apparatus determines first duration based on the sampling cycle and the occupancy of the first buffer at the first sampling moment. The first duration is duration for which a second communication apparatus stops sending data to the first communication apparatus. The first communication apparatus sends first indication information to the second communication apparatus based on the first duration.