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SubjectRe: zero-copy TCP
> You stated in an earlier message you copied the data when you caclulated
> the TCPIP checksum? No you say you don't. Perhaps I misunderstood.

We do a single copy/checksum from user space. You have to do the copy because
the packet may not be DMAable, may not be aligned for most PCI hardware and
numerous other things. Since that copy costs as much as the checksum its
effectively free in the checksum computation. It also avoids considerable
complexity on the TCP paths when you need to retransmit.

> > I don't think you've actually sat and instrumented the TCP code
> The TCPIP stack in Wolf Mountain has my name as the author, and it was

The Linux TCP code..

> one of the nastiest projects I've ever done. OSPF routing is bitch
> BTW. Try again.

OSPF is a matter of getting the graph theory right.

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