X-Git-Url: https://git.martlubbers.net/?a=blobdiff_plain;f=a2%2F1cases.tex;h=d77edb786da6c74e39a172f369e996d92f519b1f;hb=cb58c69ab4e21659e03215be3ad504ac47f80392;hp=18420a7e09e73dff808657041eb37542c84ba9d5;hpb=9d533c0f740c7f826b75286f309be9f7f3a3674d;p=tt2015.git

diff --git a/a2/1cases.tex b/a2/1cases.tex
index 18420a7..d77edb7 100644
--- a/a2/1cases.tex
+++ b/a2/1cases.tex
@@ -7,8 +7,7 @@ are to be run in a terminal. Commands prefixed with a \texttt{\#} should be run
 with root permissions. Commands prefixed with a \texttt{\$} should be run with
 user permissions.
 
-\begin{table}[H]
-\begin{tabularx}{\linewidth}{|l|X|}
+\begin{longtabu}{|l|X|}
 	\hline
 	Check 1 & Get the SUT in a workable state. \\
 	\hline
@@ -35,7 +34,6 @@ user permissions.
 		\end{enumerate}\\
 	\hline
 	Passed & \textit{Yes/No}\\
-	\hline \hline
 	Check 3 & Initialize the testing environment.\\
 	\hline
 	Course of action &
@@ -81,10 +79,8 @@ user permissions.
 	\hline
 	Passed & \textit{Yes/No}\\
 	\hline
-\end{tabularx}
-\end{table}
-
-\newpage
+	\caption{Preflight checklist\label{tbl:preflight}}
+\end{longtabu}
 
 \subsection{Testing of SUT}
 The SUT is a series of services for other computer programs with no end-user
@@ -117,13 +113,32 @@ these partitions are given.
 	\item Bits flipped in \emph{payload}
 		\begin{enumerate}
 			\item Correct payload
-			\item Payload with even number of bits flipped
+			\item Payload with bit flips 
 			\item Payload with odd number of bits flipped
 		\end{enumerate}
 	\item Correct or Incorrect \emph{checksum}
 	\item Packets received in or out of order, or missing packets
 \end{enumerate}
 
+These partitions were chosen since they correspond to key parts of the TCP
+specification. 
+
+TCP segments are send over a TCP connection from a \emph{source} to a \emph{destination port}. Therefore segments which are received which have a 
+source or destination port set to an incorrect value should not be regarded
+as segments belonging to the connection. 
+
+TCP uses a \emph{checksum} to catch any error introduced in headers, when this
+checksum does not match the actual computed checksum the packet should be
+disregarded.
+
+The TCP checksum is also an inherently weak one, as it is simply the 
+bitwise negation of the addition in ones complement arithmetic 
+of all 16 bit words in the header and data of the segment (excluding the
+header). Therefore any bit error where the ones complement value of one word
+increases by one, and the value of another decreases by one, is undetected. 
+The SUT should exhibit the same behavior and accept packets where these type
+of bit error occur.
+
 \textbf{hier iets over waarom deze partities relevant zijn! Waarom odd en 
 even number of bits flipped bijv interessant?}
 \bigskip
@@ -230,5 +245,3 @@ covered and the number of individual tests is still feasible.
 %	\end{enumerate} \\\hline
 %\end{tabularx}
 %\end{table}
-
-\newpage