\begin{frame}[fragile]
\frametitle{VPN Protocol Overview}
\begin{itemize}
\item Internet Protocol Security (IPsec)
  \begin{itemize}
  \item Internet Key Exchange (IKEv1, IKEv2)
  \item Layer 2 Tunneling Protocol (L2TP)
  \item XAUTH
  \end{itemize}
\item Transport Layer Security (TLS/SSL)
  \begin{itemize}
  \item TLS/SSL Authentication Methods
  \end{itemize}
\item Proprietary Protocols
  \begin{itemize}
  \item Generic Routing Encapsulation (GRE)
    \begin{itemize}
    \item Point-to-Point Tunneling Protocol (PPTP)
    \end{itemize}
  \end{itemize}
\end{itemize}
\end{frame}