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\title{Ip Checksum Example}
\author{Scot Anderson, Ph.D.}

\begin{document}

\maketitle

\section{Example}

\begin{tabular}{rrrrrr}
	&amp;  &amp; $0001$ &amp; $0001$ &amp;  &amp; $(17)$ \\
	$+$ &amp;  &amp; $1111$ &amp; $0111$ &amp;  &amp; $(-8)$ \\ \cline{1-4}\cline{6-6}
	&amp; $1$ &amp; $0000$ &amp; $1000$ &amp;  &amp;  \\
	&amp;  &amp; \multicolumn{1}{l}{$\hookrightarrow $} &amp; $+1$ &amp;  &amp;  \\ \cline{3-4}
	&amp;  &amp; $0000$ &amp; $1001$ &amp; $=$ &amp; $(9)$ \\
	\multicolumn{6}{l}{Hence the checksum is:} \\
	&amp;  &amp; $1111$ &amp; $0110$ &amp;  &amp;
\end{tabular}

\bigskip

If we sum up the original two numbers with the checksum we get:

\begin{tabular}{rrrr}
	&amp;  &amp; $0001$ &amp; $0001$ \\
	&amp;  &amp; $1111$ &amp; $0111$ \\
	$+$ &amp;  &amp; $1111$ &amp; $0110$ \\ \cline{1-4}
	&amp;  &amp; $11111$ &amp; $1110$%
\end{tabular}
			
Of courxse with the carry over we have:\ $1111~1111$ which is $-0.$ 

\end{document}
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