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\section{Core Network protocol implementations}
\subsection{Erlang implementations}
\begin{frame}{Erlang osmo\_ss7}
\begin{itemize}
\item Signalling link management
\item Signalling linkset management
\item MTP-level routing
\item Protocol codecs
\begin{itemize}
\item BSSMAP, ISUP, M2PA, M2UA, M3UA, MTP3, SCCP, SUA
\end{itemize}
\item Various different protocol implementations
\begin{itemize}
\item SIGTRAN: M3UA, M2PA, M2UA, SUA
\item IPA multiplex / SCCP lite
\end{itemize}
\end{itemize}
\end{frame}
\begin{frame}{Erlang osmo\_sccp}
SCCP implementation, typcially used on top of osmo\_sccp
\begin{itemize}
\item SCCP connectionless (SCLC)
\item SCCP connection oriented (SCOC)
\item SCCP routing / gtt (SCRC)
\item applications can bind to SSN numbers
\end{itemize}
\end{frame}
\begin{frame}{Erlang osmo\_map}
\begin{itemize}
\item Not a full-blown MAP end-user implementation
\item Primarily a set of integrated TCAP+MAP codec
\item Used for protocol analysis/dissection
\item Used for transparent MAP mangling engines
\item Think of FTP/IRC NAT in TCP/IP, where you need to modify
addresses contained in the payload (not header) of the
messages
\end{itemize}
\end{frame}
\begin{frame}{Erlang mgw\_nat}
\begin{itemize}
\item Strange transparent SCCP/TCAP/MAP gateway
\item Supports all kinds of strange operations
\begin{itemize}
\item SCCP Global Title Masquerade (dynamic GT pool)
\item Replace VLR/MSC GT inside MAP payload
\item Supported Camel Phase patching
\item 1:1 IMSI mapping in MAP payload
\item ISUP GT mangling
\item national/international numbering plan conversions
\end{itemize}
\item Used in multiple production installations in real operator
core network for ~ 2 years
\end{itemize}
\end{frame}
\begin{frame}{Erlang signerl TCAP}
\includegraphics[width=60mm]{osi_model.png}
\end{frame}
\begin{frame}{Erlang signerl TCAP}
\begin{itemize}
\item Full ITU-T TCAP implementation
\item 1:1 mapping of ITU-T TCAP state machines to Erlang gen\_fsm
\begin{itemize}
\item DHA - Dialogue Handling
\item TSM - Transaction State Machine
\item ISM - Invocation State Machine
\end{itemize}
\item 1:1 mapping of other ITU-T entities to Erlang gen\_server
\begin{itemize}
\item CCO - Componen Coordinator
\item TCO - Transaction Coordinator
\end{itemize}
\item Some old/incomplete/bit-rotten ANSI TCAP code
\end{itemize}
\end{frame}
\begin{frame}{Message flow among signerl TCAP Processes}
\includegraphics[width=100mm]{tcap_messaging.png}
\end{frame}
\begin{frame}{Erlang supervisor hierarchy in signerl TCAP}
\includegraphics[width=70mm]{tcap_supervision.png}
\end{frame}
\begin{frame}{Erlang signerl TCAP}
\begin{itemize}
\item properly implements the N-primitives to lower level
\item properly implements all TR-primitives internally (TC / TR
split)
\item properly implements all TC-primitives towards the TCAP user
\item Can be used on top of osmo\_sccp
\item Can be used directly by application servers or via signerl MAP
\end{itemize}
\end{frame}
\begin{frame}{Erlang signerl MAP}
\begin{itemize}
\item Interface between MAP primitives and TCAP primitives
\item Provides very little benefit over using TCAP directly
\item Not used much so far, I always use TCAP user API instead
\end{itemize}
\end{frame}
\begin{frame}{Message flow among signerl MAP Processes}
\includegraphics[width=100mm]{map_messaging.png}
\end{frame}
\begin{frame}{Erlang supervisor hierarchy in signerl TCAP}
\includegraphics[width=90mm]{map_supervision.png}
\end{frame}
\begin{frame}{Erlang application servers}
\begin{itemize}
\item No complete implementation of any GSM core network node
yet
\item Lots of testing / experimentation code for generating
single MAP transactions against existing/proprietary
core network components
\item Work on a HLR based on Mnesia DB should be starting soon
\end{itemize}
\end{frame}
%\subsection{C implementations}
%
%\begin{frame}{libosmo-sccp}
%\begin{itemize}
% \item minimalistic SCCP implementation
% \item only used inside IPA multiplex / SCCP lite
% \item no retransmissions / GT routing / translation
% \item stable, used in production (osmo-bsc)
%\end{itemize}
%\end{frame}
%
%\begin{frame}{libosmo-asn1-tcap}
%\begin{itemize}
% \item asn1c-generated TCAP codec
% \item almost no manual code
% \item built as shared library
%\end{itemize}
%\end{frame}
%
%\begin{frame}{libosmo-tcap}
%\begin{itemize}
% \item First attempt of Harald to implement TCAP (before Erlang)
% \item 1:1 mapping of ITU-T TCAP components to C source files
% \item Heavily based on asn1c-generated data structures
% \item Uses libosmo-asn1-tcap
%\end{itemize}
%\end{frame}
%
%\begin{frame}{libosmo-asn1-map}
%\begin{itemize}
% \item asn1c-generated MAP code
% \item almost no manual code
% \item built as shared library
%\end{itemize}
%\end{frame}
%
%\begin{frame}{Future of C implementation?}
%\begin{itemize}
% \item unclear at this point
% \item first finish testing/deploying Erlang implementations
% \item possible use case for Gc interface of osmo-sgsn (SGSN-HLR)
% \item Do we interface C code with Erlang MAP or maintain C implementation in parallel?
%\end{itemize}
%\end{frame}
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