diff --git a/src/libmsc/iucs_ranap.c b/src/libmsc/iucs_ranap.c
new file mode 100644
index 0000000..c016474
--- /dev/null
+++ b/src/libmsc/iucs_ranap.c
@@ -0,0 +1,104 @@
+/* Implementation of RANAP messages to/from an MSC via an Iu-CS interface.
+ * This keeps direct RANAP dependencies out of libmsc. */
+
+/* (C) 2016 by sysmocom s.m.f.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * 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 "../../bscconfig.h"
+
+#ifdef BUILD_IU
+
+#include <osmocom/core/logging.h>
+
+#include <osmocom/ranap/ranap_ies_defs.h>
+
+#include <openbsc/debug.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/gsm_subscriber.h>
+#include <openbsc/iu.h>
+#include <openbsc/iucs.h>
+#include <openbsc/vlr.h>
+#include <openbsc/iucs_ranap.h>
+#include <openbsc/osmo_msc.h>
+
+/* To continue authorization after a Security Mode Complete */
+int gsm0408_authorize(struct gsm_subscriber_connection *conn);
+
+static int iucs_rx_rab_assign(struct gsm_subscriber_connection *conn,
+			      RANAP_RAB_SetupOrModifiedItemIEs_t *setup_ies)
+{
+	uint8_t rab_id;
+	RANAP_RAB_SetupOrModifiedItem_t *item = &setup_ies->raB_SetupOrModifiedItem;
+
+	rab_id = item->rAB_ID.buf[0];
+
+	LOGP(DIUCS, LOGL_NOTICE,
+	     "Received RAB assignment event for %s rab_id=%hhd\n",
+	     vlr_subscr_name(conn->vsub), rab_id);
+
+	return 0;
+}
+
+int iucs_rx_sec_mode_compl(struct gsm_subscriber_connection *conn,
+			   RANAP_SecurityModeCompleteIEs_t *ies)
+{
+	OSMO_ASSERT(conn->via_ran == RAN_UTRAN_IU);
+
+	/* TODO evalute ies */
+
+	msc_rx_sec_mode_compl(conn);
+	return 0;
+}
+
+int iucs_rx_ranap_event(struct gsm_network *network,
+			struct ue_conn_ctx *ue_ctx, int type, void *data)
+{
+	struct gsm_subscriber_connection *conn;
+
+	conn = subscr_conn_lookup_iu(network, ue_ctx);
+
+	if (!conn) {
+		LOGP(DRANAP, LOGL_ERROR, "Cannot find subscriber for IU event %u\n", type);
+		return -1;
+	}
+
+	switch (type) {
+	case IU_EVENT_IU_RELEASE:
+	case IU_EVENT_LINK_INVALIDATED:
+		LOGP(DIUCS, LOGL_INFO, "IuCS release for %s\n",
+		     vlr_subscr_name(conn->vsub));
+		msc_subscr_conn_close(conn, 0);
+		return 0;
+
+	case IU_EVENT_SECURITY_MODE_COMPLETE:
+		LOGP(DIUCS, LOGL_INFO, "IuCS security mode complete for %s\n",
+		     vlr_subscr_name(conn->vsub));
+		return iucs_rx_sec_mode_compl(conn,
+					      (RANAP_SecurityModeCompleteIEs_t*)data);
+	case IU_EVENT_RAB_ASSIGN:
+		return iucs_rx_rab_assign(conn,
+				(RANAP_RAB_SetupOrModifiedItemIEs_t*)data);
+	default:
+		LOGP(DIUCS, LOGL_NOTICE, "Unknown message received:"
+		     " RANAP event: %i\n", type);
+		return -1;
+	}
+}
+
+#endif /* BUILD_IU */