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--- a/1intro.tex
+++ b/1intro.tex
@@ -2,36 +2,58 @@
 %1, 2
 The objective of this document is to provide an approach for testing a
 particular implementation of \textit{Transmission Control Protocol} (TCP). TCP
-is a host-to-host protocol that provides a reliable communication. 
+is a host-to-host protocol that provides a reliable communication.
 
 This testing approach can be used by either an internal test team or an
 independent testing team. The test effort's goal is to become confident about
-the conformance of the implementation to the specification created by
+the conformance of an existing implementation to the specification created by
 \textit{The Internet Engineering Task Force}
 (IETF)\footnote{\url{http://www.ietf.org}} as document
-\textit{RFC793}~\cite{rfc793}.
+\textit{RFC793}~\cite{rfc793}. This document is explicitly \emph{not} intended
+to serve as guideline for testing during the development phase, but for testing
+conformity to the specification of an \emph{existing} implementation.
 
 \subsection{SUT}
 %3,4
-The \textit{System under test} (SUT) is a
-Java\footnote{\url{http://www.java.com}} TCP driven echo server that executed
-on a virtualized Ubuntu system\footnote{\url{http://www.ubuntu.com}} running on
-the Linux kernel\footnote{\url{http://www.kernel.org}} version $3.13$. To test
-the error behaviour custom iptables output policies have to be
-set~\ref{listing:iptables}.
+\includegraphics[width=\linewidth]{SUTsetup.eps}
 
-\begin{lstlisting}[label={listing:iptables},caption={settings iptables}]
-Chain OUTPUT (policy ACCEPT)
-target	prot	opt	source	destination
-ACCEPT	tcp	--	anywhere	anywhere	tcp flags:PSH/PSH
-DROP	tcp	--	anywhere	anywhere	tcp flags:RST/RST
-\end{lstlisting}
+The \textit{System under test} (SUT) is the TCP implementation of a system
+running a Linux kernel\footnote{\url{http://www.kernel.org}} version $3.13$.
+TCP is not a program that runs on its own and therefore we have to make use of
+some tools to be able to test the protocol. This is further described in
+Section~\ref{section:testenv}.
 
-\subsection{Risks}
-%5. Risks
-Risks can be divided into two categories. Project risks and Product risks.
+The specification of TCP is too big to be tested in one go so we focus on
+specific sections from \textit{RFC793}.
 \begin{itemize}
-	\item\textbf{Project Risks}\\
-	\item\textbf{Product Risks}\\
+	\item Sequence numbers~\cite[Section~3.3]{rfc793}.
+	\item Setting up a connection via the 
+		``Three-way handshake''~\cite[Section~3.4]{rfc793}.
+	\item Closing a connection~\cite[Section~3.5]{rfc793}.
+	\item Data communication~\cite[Section~3.7]{rfc793}.
 \end{itemize}
 
+\subsection{Risks}
+\label{sec:risks}
+%5. Risks
+Risks can be divided into two categories. Project risks and product risks.
+Because an existing implementation is tested the project risks are non
+applicable. Product risks however are very important since it is unknown if the
+product has been tested during development.
+
+The product risks for the SUT are significant because misbehaviour of the SUT
+could have potential large consequences. The key characteristics of TCP are
+integrity and reliability~\cite[Section~1]{rfc793}, these characteristics cease
+to exist when the implementation is faulty.
+
+Because TCP is a core functionality of a networking capable system it is
+crucial that the TCP implementation functions according to the specification.
+Several critical systems could rely on the correct functionality of the TCP
+implementation. A failure in the SUT could therefore have extensive
+consequences. Even more so since TCP is a computer-to-computer protocol, which
+leaves no room for ambiguity, which could be solved in a computer-to-human
+protocol. Another effect of the SUT being a computer-to-computer protocol
+without a standalone program is the fact that we can only observe the SUT
+indirectly. With the use of tools we can see what the output is for a given
+input but there is always the risk that the tools give an incomplete or faulty
+view of the output.