Intro: added explenation why iptables are needed

diff --git a/1intro.tex b/1intro.tex
index 7da3120..1faf5c8 100644 (file)
--- a/1intro.tex
+++ b/1intro.tex
@@ -18,7 +18,9 @@ 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}.
+set Listing~\ref{listing:iptables}. This is needen because the OS by default 
+closes all connections from unknown sources and the manually created TCP 
+connections used in testing the implementation are unknown to the OS.
 
 \begin{lstlisting}[label={listing:iptables},caption={settings iptables}]
 Chain OUTPUT (policy ACCEPT)