\begin{frame}[fragile]
\frametitle{VPN Product Overview}
\begin{itemize}
\item Internet Protocol Security (IPsec)
  \begin{itemize}
  \item openSWAN
  \item strongSWAN
  \item openL2TP
  \item Mac OS X (built-in)
  \end{itemize}
\item Transport Layer Security (TLS/SSL)
  \begin{itemize}
  \item openVPN
  \end{itemize}
\item Point-to-Point Tunneling Protocol (PPTP)
  \begin{itemize}
  \item Poptop (pptpd)
  \item Microsoft Windows XP and later (built-in)
  \end{itemize}
\item Commercial Products
  \begin{itemize}
  \item various Closed Source Software Solutions (e.g. Cisco)
  \item various Hardware-based Solutions (e.g. Juniper, Sophos)
  \end{itemize}
\end{itemize}
\end{frame}