%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 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}. This document is explicitly \emph{not} intented
-to serve as guideline for testing during the development phase, but for testing
-conformatiy to the specification of an \emph{existing} implementation.
+\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 Listing~\ref{listing:iptables}. This is needed because the kernel by default
-closes all connections from unknown sources and the manually created TCP
-packets used in testing the implementation are from a source unknown to the
-kernel.
-
-\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}
-
-\subsection{Risks} \label{sec:risks}
+
+\includegraphics[width=\linewidth]{SUTsetup}
+
+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}.
+
+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 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 used the project risk are non applicable.
-Product risks even more so, since it is unknown if the product has been
-tested during development.
+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{rfc793}, these characteristics cease to exist
-when the implementation is faulty.
+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.
-
-
-
+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.
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