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SubjectRe: zero-copy TCP
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>>>>> "Jeff" == Jeff V Merkey <jmerkey@timpanogas.com> writes:

Jeff> **ALL** Netware network drivers support a scatter/gather
Jeff> proramming interface, whether the hardware does or not. In
Jeff> NetWare, the drivers get passed a fragment list in what's called
Jeff> an ECB (Event Control Block). It's the drivers responsiblity to
Jeff> assemble the fragment lists. We did it this way to support
Jeff> scatter/gather cards and non-scatter gather cards in one
Jeff> interface. Those drivers that do not support scatter gather DMA
Jeff> operations copy to a local buffer to assemble the packet. Those
Jeff> with a shared memory window copy data from the fragment list
Jeff> into this window until a complete IEEE frame gets completed
Jeff> (since it will get copied anyway), then hit the register bits to
Jeff> initiate a send of the data.

You just told us earlier in the thread that NetWare does direct zero
copy DMA but thats only half the story obviously. Up until the era of
Gigabit Ethernet cards there were almost no PCI cards available that
would do scatter/gather so obviously netware wasn't doing zero copy
either.

Jes
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