Abstract: A fly-by checksum is generated at a lower layer of the protocol stack and travels up to a high layer of a protocol stack to verify incoming data. In one embodiment, a network adapter comprises includes one or more protocol stacks and a LAN controller that includes a fly-by checksum generation unit. A checksum algorithm is registered with the fly-by checksum generation unit for each protocol layer that is to receive a fly-by checksum. As an incoming packet is transferred from network media to network adapter memory, the fly-by checksum generation unit calculates a fly-by checksum for each checksum algorithm that has been registered. After the fly-by checksums are complete, they are transmitted to the network adapter memory and are transmitted up the appropriate protocol stack within a checksum channel. When data reaches a layer of the protocol stack for which the fly-by checksum was generated, the fly-by checksum is removed from the checksum channel and is used to verify the integrity of the data.