diff --git a/public-trunk/GSM/Makefile.am b/public-trunk/GSM/Makefile.am
index da5a7fa..1002691 100644
--- a/public-trunk/GSM/Makefile.am
+++ b/public-trunk/GSM/Makefile.am
@@ -32,6 +32,7 @@ libGSML1_la_SOURCES = \
 	GSML1FEC.cpp \
 	GSMTDMA.cpp \
 	GSMTransfer.cpp \
+	OsmoSAPMux.cpp \
 	GSMTAPDump.cpp
 
 libGSM_la_SOURCES = \
@@ -77,5 +78,6 @@ noinst_HEADERS = \
 	GSMTransfer.h \
 	PowerManager.h \
 	GSMTAPDump.h \
+	OsmoSAPMux.h \
 	gsmtap.h
 
diff --git a/public-trunk/GSM/OsmoSAPMux.cpp b/public-trunk/GSM/OsmoSAPMux.cpp
new file mode 100644
index 0000000..8eb307b
--- /dev/null
+++ b/public-trunk/GSM/OsmoSAPMux.cpp
@@ -0,0 +1,50 @@
+/*
+* Copyright 2011 Harald Welte <laforge@gnumonks.org>
+*
+* This software is distributed under the terms of the GNU Affero Public License.
+* See the COPYING file in the main directory for details.
+*
+* This use of this software may be subject to additional restrictions.
+* See the LEGAL file in the main directory for details.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+
+
+#include "OsmoSAPMux.h"
+#include "GSMTransfer.h"
+#include "GSML1FEC.h"
+
+#include <Logger.h>
+
+
+using namespace GSM;
+
+
+void OsmoSAPMux::writeHighSide(const L2Frame& frame)
+{
+	// The SAP may or may not be present, depending on the channel type.
+	OBJLOG(DEEPDEBUG) << "OsmoSAPMux::writeHighSide " << frame;
+}
+
+
+
+void OsmoSAPMux::writeLowSide(const L2Frame& frame)
+{
+	OBJLOG(DEEPDEBUG) << "OsmoSAPMux::writeLowSide SAP" << frame.SAPI() << " " << frame;
+}
+
+// vim: ts=4 sw=4
diff --git a/public-trunk/GSM/OsmoSAPMux.h b/public-trunk/GSM/OsmoSAPMux.h
new file mode 100644
index 0000000..5a16f05
--- /dev/null
+++ b/public-trunk/GSM/OsmoSAPMux.h
@@ -0,0 +1,70 @@
+/*
+* Copyright 2011 Harald Welte <laforge@gnumonks.org>
+*
+* This software is distributed under the terms of the GNU Affero Public License.
+* See the COPYING file in the main directory for details.
+*
+* This use of this software may be subject to additional restrictions.
+* See the LEGAL file in the main directory for details.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+
+
+#ifndef OsmoSAPMUX_H
+#define OsmoSAPMUX_H
+
+#include "GSMSAPMux.h"
+#include "GSMTransfer.h"
+#include "GSML1FEC.h"
+
+#include <Logger.h>
+
+namespace GSM {
+
+/**
+	A SAPMux is a multipexer the connects a single L1 to multiple L2s.
+	A "service access point" in GSM/ISDN is analogous to port number in IP.
+	GSM allows up to 4 SAPs, although only two are presently used.
+	See GSM 04.05 5.2 for an introduction.
+*/
+class OsmoSAPMux : public SAPMux {
+
+	protected:
+
+	public:
+
+	OsmoSAPMux(){ 
+	}
+
+	virtual ~OsmoSAPMux() {}
+
+	virtual void writeHighSide(const L2Frame& frame);
+	virtual void writeLowSide(const L2Frame& frame);
+
+	void upstream( L2DL * wUpstream, unsigned wSAPI=0 )
+		{ }
+	void downstream( L1FEC * wDownstream )
+		{ }
+
+};
+
+
+}	// namespace GSM
+
+
+#endif
+// vim: ts=4 sw=4