A method and device for a flow control over network devices includes a receiving end device and a transmitting end device. The receiving end device monitors an input buffer and determines whether an available space in the input buffer is less than a predetermined threshold. Upon determining that the available space in the input buffer is less than the predetermined threshold, the receiving end device sets, in a MAC control code, an identifier that indicates an extended pause frame, and transmits the extended pause frame to the transmitting end device. The receiving end device also sets, in a stop time period field, output control data to control data transmission for each class based on the available space in the input buffer. Based on the output control data of the extended pause frame transmitted from the receiving end device, the transmitting end device exercises band control for each priority class.