On Mar 23, 12:59am, patrick@klos.com wrote:
} 
} I have a question about the IP header checksum that I'm looking for a
} definitive answer for.  I'm pretty sure I have the answer, but if anyone 
} can help me substantiate my answer, it would really help.
} 
} The IP header checksum is pretty straightforward: add up all the (2 byte)
} words in the IP header using one's complement addition, then take the one's
} complement of the sum and insert that as the checksum.  Here's the question:
} 
}     Is it proper to substitute a resulting value of 0x0000 with 0xffff as 
}     is done in UDP?

     No.  This question could easily be answered by checking the RFC
for IP (it is fairly easy to read).  See
ftp://ftp.rfc-editor.org/in-notes/rfc791.txt .

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     Interesting that you are advertising something like this when you
have to ask trivial questions about the most commonly used protocol!

}-- End of excerpt from patrick@klos.com