A method includes determining a first data sending rate based on multiple round-trip times (RTTs), where the multiple RTTs include RTTs of a plurality of first probe packets sent at different sending rates, and the first sending rate is a sending rate corresponding to an RTT that is in the multiple RTTs and that is less than a first preset threshold; determining a second sending rate based on a plurality of packet loss rates, where the packet loss rates include packet loss rates of a plurality of second probe packets sent at different sending rates, and the second sending rate is a sending rate corresponding to a packet loss rate that is less than a second preset threshold; and sending a third probe packet at a third sending rate.