In an example, a logic apparatus of an interface board in a network device may generate an Ethernet flow control packet including sending completion information according to Ethernet data packets sent from a sending buffering queue maintained in the interface board. The logic apparatus of the interface board may transmit the Ethernet flow control packet including sending completion information to an Ethernet data channel by taking priority over Ethernet data packets in a receiving buffering queue in an ingress direction. The sending completion information is used by a CPU of a mainboard to maintain a state of the sending buffering queue.