The present invention discloses an apparatus and method for performing cyclic redundancy check (CRC) on partial protocol data units (PDUs). The disclosed apparatus is designed to off-load the CRC calculation for transmit or receive from a host computer. According to the disclosed method, when generating CRC for partial PDUs, for each such PDUs a decision is made to determine whether a CRC action is required, i.e., if CRC should be calculated, checked or placed in the outgoing byte stream. When partial CRC calculation is performed the intermediate value is saved into memory and later is used for calculating the CRC for a consecutive partial PDU. In accordance with a preferred embodiment of the invention, the need to re-calculate the CRC in a case of a re-transmit request is eliminated.