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Re: TCP Checksum Interoperability

2002-04-05 12:30:37
The last time this came up for a TCP implementation I used to
maintain, our interpretation of Robustness Principle applied to this
problem dictated that we shouldn't send segments with checksum fields
set to all ones (that is, we shouldn't send ~(+0)), but that we had to
accept either ~(+0) or ~(-0) in received segments.

Strictly speaking, either zero state is completely legal, but one is
(apparently) more surprising to most implementors than the other, due
to the implementation techniques that suggest themselves on most
modern processors.



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