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SubjectRe: zero-copy TCP fileserving
Richard B. Johnson wrote:
> It looks as though the normal CRC is appended during the actual transmit.
> If the offset of the checksum was known to a controller, it could fill in
> the checksum using the same mechanism.

The difference is the Ethernet CRC goes at the end of the frame
(designed for insertion by hardware), but the TCP/UDP data checksums go
_before_ the data.

So hardware has to buffer an entire frame before it can insert the
TCP/UDP checksum. As most (if not all) network drivers do load the
entire frame onto the card before beginning transmission, this is a
possibility.

-- Jamie

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