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diff --git a/2010/gsm_foss-mt2010/section-openbsc.tex b/2010/gsm_foss-mt2010/section-openbsc.tex new file mode 100644 index 0000000..0c1b9f4 --- /dev/null +++ b/2010/gsm_foss-mt2010/section-openbsc.tex @@ -0,0 +1,200 @@ +\section{OpenBSC} + +%\subsection{OpenBSC Introduction} + +\begin{frame}{OpenBSC software} +OpenBSC is a Open Source implementation of (not only) the BSC features +of a GSM network. +\begin{itemize} + \item Support A-bis interface over E1 and IP + \item Support for BTS vendor/model is modular, currently Siemens BS-11 and ip.access nanoBTS + \item Multiple BTS models/vendorrs can be mixed! + \item Can work as a {\em pure BSC} or as a full {\em network in a box} + \item Supports mobility management, authentication, intra-BSC hand-over, SMS, voice calls (FR/EFR/AMR) + \item GPRS + EDGE support if combined with OsmoSGSN and OpenGGSN +\end{itemize} +\end{frame} + +\begin{frame}{OpenBSC} +\begin{itemize} + \item Supports Siemens BS-11 BTS (E1) and ip.access nanoBTS (IP based) + \item Has classic 2G signalling, voice and SMS support + \item Implements various GSM protocols like + \begin{itemize} + \item A-bis RSL (TS 08.58) and OML (TS 12.21) + \item TS 04.08 Radio Resource, Mobility Management, Call Control + \item TS 04.11 Short Message Service + \end{itemize} + \item Telnet console with Cisco-style interface +\end{itemize} +\end{frame} + +\begin{frame}{OpenBSC software architecture} +\begin{itemize} + \item Implemented in pure C, similarities to Linux kernel + \begin{itemize} + \item Linked List handling, Timer API, coding style + \end{itemize} + \item Single-threaded event-loop / state machine design + \item Telnet based command line interface {\em Cisco-style} + \item Input driver abstraction (mISDN, Abis-over-IP) +\end{itemize} +\end{frame} + +\begin{frame}{OpenBSC: GSM network protocols}{The A-bis interface} + \begin{description}[Layer 4+] + \item[Layer 1] Typically E1 line, TS 08.54 + \item[Layer 2] A variant of ISDN LAPD with fixed TEI's, TS 08.56 + \item[Layer 3] OML (Organization and Maintenance Layer, TS 12.21) + \item[Layer 3] RSL (Radio Signalling Link, TS 08.58) + \item[Layer 4+] transparent messages that are sent to the MS via Um + \end{description} +\end{frame} + +%\begin{frame}{OpenBSC: How it all started} +%\begin{itemize} +% \item In 2006, I bought a Siemens BS-11 microBTS on eBay +% \begin{itemize} +% \item This is GSM900 BTS with 2 TRX at 2W output power (each) +% \item A 48kg monster with attached antenna +% \item 200W power consumption, passive cooling +% \item E1 physical interface +% \end{itemize} +% \item I didn't have much time at the time (day job at Openmoko) +% \item Started to read up on GSM specs whenever I could +% \item Bought a HFC-E1 based PCI E1 controller, has mISDN kernel support +% \item Found somebody in the GSM industry who provided protocol traces +%\end{itemize} +%\end{frame} + +%\begin{frame}{OpenBSC: Timeline} +%\begin{itemize} +% \item In November 2008, I started the development of OpenBSC +% \item In December 2008, we did a first demo at 25C3 +% \item In January 2009, we had full voice call support +% \item In June 2009, I started with actual security related stuff +% \item In August 2009, we had the first field test with 2BTS and > 860 phones +%\end{itemize} +%\end{frame} + +\begin{frame}{OpenBSC: Field Test at HAR2009} +\begin{figure}[h] +\subfigure{\includegraphics[width=5cm]{bts_tree_full.jpg}} +\subfigure{\includegraphics[width=5cm]{openbsc_host.jpg}} +\end{figure} +\end{frame} + + +\subsection{OpenBSC Network In The Box} + +\begin{frame}{OpenBSC in NITB mode}{Network In a Box Mode} +The {\tt bsc\_hack} program +\begin{itemize} + \item implements the A-bis interface towards any number of BTS + \item provides most typical features of a GSM network in one software + \item no need for MSC, AuC, HLR, VLR, EIR, ... + \begin{itemize} + \item HLR/VLR as SQLite3 table + \item Authentication + Ciphering support + \item GSM voice calls, MO/MT SMS + \item Hand-over between all BTS + \item Multiple Location Areas within one BSC + \end{itemize} +\end{itemize} +\end{frame} + +\begin{frame}{OpenBSC NITB features} +OpenBSC NITB features +\begin{itemize} + \item Run a small GSM network with 1-n BTS and OpenBSC + \item No need for MSC/HLR/AUC/... + \item No need for your own SIM cards (unless crypto/auth rqd) + \item Establish signalling and voice channels + \item Make incoming and outgoing voice calls between phones + \item Send/receive SMS between phones + \item Connect to ISDN PBX or public ISDN via Linux Call Router +\end{itemize} +\end{frame} + +\begin{frame}{OpenBSC in NITB mode}{Network In a Box Mode} +The {\tt bsc\_hack} program +\begin{itemize} + \item does not implement any other GSM interfaces apart from A-bis + \item no SS7 / TCAP / MAP based protocols + \item no integration (roaming) with existing traditional GSM networks + \item wired telephony interfacing with ISDN PBX {\tt lcr} (Linux Call Router) + \item Has been tested with up to 800 subscribers on 5 BTS + \item Intended for R\&D use or private PBX systems +\end{itemize} +\end{frame} + +\begin{frame}{OpenBSC LCR integration}{Interfacing with wired telephony} +OpenBSC (NITB mode) can be linked into Linux Call Router ({\tt lcr}) +\begin{itemize} + \item OpenBSC is compiled as libbsc.a + \item libbsc.a includes full OpenBSC NITB mod code + \item linking the library into {\tt lcr} results in GSM {\em line interfaces} to become available inside {\tt lcr} + \item OpenBSC no longer takes care of call control, but simply hands everything off to {\tt lcr} + \item Dialling plan, etc. is now configure in {\tt lcr} like for any other wired phones +\end{itemize} +\end{frame} + +\subsection{OpenBSC BSC-only mode} + +\begin{frame}{OpenBSC in BSC-only mode} +The {\tt osmo-bsc} program +\begin{itemize} + \item behaves like a classic GSM BSC + \item uses SCCP-Lite (ip.access multipex) to any SoftMSC like ADC + \item used in production/commercial deployments (~ 75 BSCs) + \item mainly intended to replace proprietary BSC in traditional GSM networks +\end{itemize} +\end{frame} + +\begin{frame}<handout:0>{OpenBSC} + Demonstration +\end{frame} + +\subsection{OpenBSC GPRS support} + +\begin{frame}{GPRS and OpenBSC} +\begin{itemize} + \item The BSC doesn't really do anything related to GPRS + \item GPRS implemented in separate SGSN and GGSN nodes + \item GPRS uses its own Gb interface to RAN, independent of A-bis + \item OpenBSC can configure the nanoBTS for GPRS+EDGE support via OML + \item Actual SGSN and GGSN implemented as OsmoSGSN and OpenGGSN programs +\end{itemize} +\end{frame} + +\begin{frame}{OsmoSGSN} +The Osmocom SGSN program implements +\begin{itemize} + \item basic/minimal SGSN functionality + \item the Gb interface (NS/BSSGP/LLC/SNDCP) + \item mobility management, session management +\end{itemize} +It's a work in progress, many missing features +\begin{itemize} + \item no HLR integration yet + \item no paging coordination with MSC/BSC + \item no encryption support yet +\end{itemize} +\end{frame} + +\begin{frame}{OpenGGSN} +\begin{itemize} + \item GPL licensed Linux program implementing GGSN node + \item Implements GTP-U protocol between SGSN and GGSN + \item User-configurable range/pool of IPv4 addresses for MS + \item Uses {\tt tun} device for terminating IP tunnel from MS + \item provides GTP implementation as libgtp + \item Experimental patches for IPv6 support +\end{itemize} +\end{frame} + +%\begin{frame}<handout:0>{OpenBSC + OpenGGSN + OsmoSGSN} +% Demonstration +%\end{frame} + +% FIXME: include slide showing full OpenBSC+OsmoSGSN+OpenGGSN network |