\begin{frame}[fragile]
\frametitle{free/open/strongSWAN}
\begin{itemize}
\item most flexible product: strongSWAN
\item based on Internet Protocol Security (IPsec)
\item support for IKEv1/v2, L2TP, and XAuth
\item Pros:
  \begin{itemize}
  \item flexible configuration
  \item support for nearly all authentication methods described in standard
  \item very high security level
  \end{itemize}
\item Cons:
  \begin{itemize}
  \item complex configuration
  \item setup requires knowledge of underlying Network topology
  \item problems with IKEv1 in NAT topologies
  \end{itemize}
\end{itemize}
\end{frame}