Re: [lwip-users] TCP retransmissions and duplicate ACKs

[dii]

Hi Niall,

Thanks for the lead.

I checked my driver setup and found that the transmit threshold was left at
the default of 64. But then I also read in the processor reference that the
threshold is not used in store-and-forward mode, which is what I use for
checksum offloading. In store-and-forward mode, transmission starts as soon
as a full frame resides in the Transmit FIFO (MCU dedicated 2kB). It gets
there through a DMA transfer. The MAC expects full frames, and that is what
the ethernet driver sets up, and that is what the netif_low_level_output()
passes to the ethernet driver... So that all looks fine to me.

Going to add some code to try to trace lwip ACK generation through to the
MAC...



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