A network interface controller is provided, including a receiving module, a boundary determination module, a first checksum calculation module, and a second checksum calculation module. The receiving module receives a packet having a segment of a first layer protocol and a segment of a second layer protocol. The boundary determination module performs a boundary determination operation on the packet to generate boundary information, wherein the boundary information includes a length of the segment of the second layer protocol and a boundary indication signal. The first checksum calculation module finishes the calculation of a first checksum corresponding to the segment of the first layer protocol after receiving the length of the segment of the second layer protocol. The second checksum calculation module starts to calculate a second checksum corresponding to the segment of the second layer protocol after receiving the boundary indication signal.