Re: How to disable software TCP checksumming?

[Bill Fenner]

>The TCP checksum protects more than just the contents of the packet
>on the wire; it's also a (somewhat) weak check on the contents
>of your packet sitting in memory, and as it's going over the bus
>in your computer between memory and peripherals and for other end-to-end
>sorts of issues. 

In fact, Jonathan Stone at Stanford did some measurements of checksum
errors for his thesis, and found that on a given link in the Stanford
residences there were a surprising (small, but measurable) number of
packets with IP header checksum errors with what appeared to be DMA errors
-- e.g. 4 bytes missing from the middle of the header.  When the end to
end checksum is really memory to memory, it can catch errors like this...

  Bill

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