diff --git a/src/libmsc/a_iface_bssap.c b/src/libmsc/a_iface_bssap.c
new file mode 100644
index 0000000..561ccde
--- /dev/null
+++ b/src/libmsc/a_iface_bssap.c
@@ -0,0 +1,717 @@
+/* (C) 2017 by Sysmocom s.f.m.c. GmbH
+ * All Rights Reserved
+ *
+ * Author: Philipp Maier
+ *
+ * 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 <osmocom/core/utils.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/sigtran/sccp_helpers.h>
+#include <osmocom/sccp/sccp_types.h>
+#include <osmocom/gsm/gsm0808.h>
+#include <osmocom/gsm/gsm0808_utils.h>
+#include <openbsc/debug.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/a_iface_bssap.h>
+#include <openbsc/a_iface.h>
+#include <openbsc/iu.h>
+#include <openbsc/osmo_msc.h>
+#include <osmocom/core/byteswap.h>
+#include <openbsc/a_reset.h>
+
+#define IP_V4_ADDR_LEN 4
+
+/*
+ * Helper functions to lookup and allocate subscribers
+ */
+
+/* Allocate a new subscriber connection */
+static struct gsm_subscriber_connection *subscr_conn_allocate_a(const struct a_conn_info *a_conn_info,
+								struct gsm_network *network,
+								uint16_t lac, struct osmo_sccp_user *scu, int conn_id)
+{
+	struct gsm_subscriber_connection *conn;
+
+	LOGP(DMSC, LOGL_NOTICE, "Allocating A-Interface subscriber conn: lac %i, conn_id %i\n", lac, conn_id);
+
+	conn = talloc_zero(network, struct gsm_subscriber_connection);
+	if (!conn)
+		return NULL;
+
+	conn->network = network;
+	conn->via_ran = RAN_GERAN_A;
+	conn->lac = lac;
+
+	conn->a.conn_id = conn_id;
+	conn->a.scu = scu;
+
+	/* Also backup the calling address of the BSC, this allows us to
+	 * identify later which BSC is responsible for this subscriber connection */
+	memcpy(&conn->a.bsc_addr, a_conn_info->bsc_addr, sizeof(conn->a.bsc_addr));
+
+	llist_add_tail(&conn->entry, &network->subscr_conns);
+	LOGP(DMSC, LOGL_NOTICE, "A-Interface subscriber connection successfully allocated!\n");
+	return conn;
+}
+
+/* Return an existing A subscriber connection record for the given
+ * connection IDs, or return NULL if not found. */
+static struct gsm_subscriber_connection *subscr_conn_lookup_a(const struct gsm_network *network, int conn_id)
+{
+	struct gsm_subscriber_connection *conn;
+
+	OSMO_ASSERT(network);
+
+	DEBUGP(DMSC, "Looking for A subscriber: conn_id %i\n", conn_id);
+
+	/* FIXME: log_subscribers() is defined in iucs.c as static inline, if
+	 * maybe this function should be public to reach it from here? */
+	/* log_subscribers(network); */
+
+	llist_for_each_entry(conn, &network->subscr_conns, entry) {
+		if (conn->via_ran == RAN_GERAN_A && conn->a.conn_id == conn_id) {
+			DEBUGP(DIUCS, "Found A subscriber for conn_id %i\n", conn_id);
+			return conn;
+		}
+	}
+	DEBUGP(DMSC, "No A subscriber found for conn_id %i\n", conn_id);
+	return NULL;
+}
+
+/*
+ * BSSMAP handling for UNITDATA
+ */
+
+/* Endpoint to handle BSSMAP reset */
+static void bssmap_rx_reset(struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	struct gsm_network *network = a_conn_info->network;
+	struct osmo_ss7_instance *ss7;
+
+	ss7 = osmo_ss7_instance_find(network->a.cs7_instance);
+	OSMO_ASSERT(ss7);
+
+	LOGP(DMSC, LOGL_NOTICE, "Rx RESET from BSC %s, sending RESET ACK\n",
+	     osmo_sccp_addr_name(ss7, a_conn_info->bsc_addr));
+	osmo_sccp_tx_unitdata_msg(scu, a_conn_info->msc_addr, a_conn_info->bsc_addr, gsm0808_create_reset_ack());
+
+	/* Make sure all orphand subscriber connections will be cleard */
+	a_clear_all(scu, a_conn_info->bsc_addr);
+
+	msgb_free(msg);
+}
+
+/* Endpoint to handle BSSMAP reset acknowlegement */
+static void bssmap_rx_reset_ack(const struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info,
+				struct msgb *msg)
+{
+
+	struct gsm_network *network = a_conn_info->network;
+	struct osmo_ss7_instance *ss7;
+
+	ss7 = osmo_ss7_instance_find(network->a.cs7_instance);
+	OSMO_ASSERT(ss7);
+
+	if (a_conn_info->reset == NULL) {
+		LOGP(DMSC, LOGL_ERROR, "Received RESET ACK from an unknown BSC %s, ignoring...\n",
+		     osmo_sccp_addr_name(ss7, a_conn_info->bsc_addr));
+		goto fail;
+	}
+
+	LOGP(DMSC, LOGL_NOTICE, "Received RESET ACK from BSC %s\n", osmo_sccp_addr_name(ss7, a_conn_info->bsc_addr));
+
+	/* Confirm that we managed to get the reset ack message
+	 * towards the connection reset logic */
+	a_reset_ack_confirm(a_conn_info->reset);
+
+fail:
+	msgb_free(msg);
+}
+
+/* Handle UNITDATA BSSMAP messages */
+static void bssmap_rcvmsg_udt(struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	/* Note: When in the MSC role, RESET ACK is the only valid message that
+	 * can be received via UNITDATA */
+
+	if (msgb_l3len(msg) < 1) {
+		LOGP(DMSC, LOGL_NOTICE, "Error: No data received -- discarding message!\n");
+		return;
+	}
+
+	LOGP(DMSC, LOGL_NOTICE, "Rx BSC UDT BSSMAP %s\n", gsm0808_bssmap_name(msg->l3h[0]));
+
+	switch (msg->l3h[0]) {
+	case BSS_MAP_MSG_RESET:
+		bssmap_rx_reset(scu, a_conn_info, msg);
+		break;
+	case BSS_MAP_MSG_RESET_ACKNOWLEDGE:
+		bssmap_rx_reset_ack(scu, a_conn_info, msg);
+		break;
+	default:
+		LOGP(DMSC, LOGL_NOTICE, "Unimplemented message format: %s -- message discarded!\n",
+		     gsm0808_bssmap_name(msg->l3h[0]));
+		msgb_free(msg);
+	}
+}
+
+/* Receive incoming connection less data messages via sccp */
+void sccp_rx_udt(struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	/* Note: The only valid message type that can be received
+	 * via UNITDATA are BSS Management messages */
+	struct bssmap_header *bs;
+
+	OSMO_ASSERT(scu);
+	OSMO_ASSERT(a_conn_info);
+	OSMO_ASSERT(msg);
+
+	LOGP(DMSC, LOGL_NOTICE, "Rx BSC UDT: %s\n", osmo_hexdump(msgb_l2(msg), msgb_l2len(msg)));
+
+	if (msgb_l2len(msg) < sizeof(*bs)) {
+		LOGP(DMSC, LOGL_ERROR, "Error: Header is too short -- discarding message!\n");
+		msgb_free(msg);
+		return;
+	}
+
+	bs = (struct bssmap_header *)msgb_l2(msg);
+	if (bs->length < msgb_l2len(msg) - sizeof(*bs)) {
+		LOGP(DMSC, LOGL_ERROR, "Error: Message is too short -- discarding message!\n");
+		msgb_free(msg);
+		return;
+	}
+
+	switch (bs->type) {
+	case BSSAP_MSG_BSS_MANAGEMENT:
+		msg->l3h = &msg->l2h[sizeof(struct bssmap_header)];
+		bssmap_rcvmsg_udt(scu, a_conn_info, msg);
+		break;
+	default:
+		LOGP(DMSC, LOGL_ERROR,
+		     "Error: Unimplemented message type: %s -- message discarded!\n", gsm0808_bssmap_name(bs->type));
+		msgb_free(msg);
+	}
+}
+
+/*
+ * BSSMAP handling for connection oriented data
+ */
+
+/* Endpoint to handle BSSMAP clear request */
+static int bssmap_rx_clear_rqst(struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	struct gsm_network *network = a_conn_info->network;
+	struct tlv_parsed tp;
+	int rc;
+	struct msgb *msg_resp;
+	uint8_t cause;
+	struct gsm_subscriber_connection *conn;
+
+	LOGP(DMSC, LOGL_NOTICE, "BSC requested to clear connection (conn_id=%i)\n", a_conn_info->conn_id);
+
+	tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l3h + 1, msgb_l3len(msg) - 1, 0, 0);
+	if (!TLVP_PRESENT(&tp, GSM0808_IE_CAUSE)) {
+		LOGP(DMSC, LOGL_ERROR, "Cause code is missing -- discarding message!\n");
+		goto fail;
+	}
+	cause = TLVP_VAL(&tp, GSM0808_IE_CAUSE)[0];
+
+	/* Respond with clear command */
+	msg_resp = gsm0808_create_clear_command(GSM0808_CAUSE_CALL_CONTROL);
+	rc = osmo_sccp_tx_data_msg(scu, a_conn_info->conn_id, msg_resp);
+
+	/* If possible, inform the MSC about the clear request */
+	conn = subscr_conn_lookup_a(network, a_conn_info->conn_id);
+	if (!conn)
+		goto fail;
+	msc_clear_request(conn, cause);
+
+	msgb_free(msg);
+	return rc;
+
+fail:
+	msgb_free(msg);
+	return -EINVAL;
+}
+
+/* Endpoint to handle BSSMAP clear complete */
+static int bssmap_rx_clear_complete(struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	int rc;
+
+	LOGP(DMSC, LOGL_NOTICE, "Releasing connection (conn_id=%i)\n", a_conn_info->conn_id);
+	rc = osmo_sccp_tx_disconn(scu, a_conn_info->conn_id,
+				  a_conn_info->msc_addr, SCCP_RELEASE_CAUSE_END_USER_ORIGINATED);
+
+	/* Remove the record from the list with active connections. */
+	a_delete_bsc_con(a_conn_info->conn_id);
+
+	msgb_free(msg);
+	return rc;
+}
+
+/* Endpoint to handle layer 3 complete messages */
+static int bssmap_rx_l3_compl(struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	struct tlv_parsed tp;
+	struct {
+		uint8_t ident;
+		struct gsm48_loc_area_id lai;
+		uint16_t ci;
+	} __attribute__ ((packed)) lai_ci;
+	uint16_t mcc;
+	uint16_t mnc;
+	uint16_t lac;
+	uint8_t data_length;
+	const uint8_t *data;
+	int rc;
+
+	struct gsm_network *network = a_conn_info->network;
+	struct gsm_subscriber_connection *conn;
+
+	LOGP(DMSC, LOGL_NOTICE, "BSC has completed layer 3 connection (conn_id=%i)\n", a_conn_info->conn_id);
+
+	tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l3h + 1, msgb_l3len(msg) - 1, 0, 0);
+	if (!TLVP_PRESENT(&tp, GSM0808_IE_CELL_IDENTIFIER)) {
+		LOGP(DMSC, LOGL_ERROR, "Mandatory CELL IDENTIFIER not present -- discarding message!\n");
+		goto fail;
+	}
+	if (!TLVP_PRESENT(&tp, GSM0808_IE_LAYER_3_INFORMATION)) {
+		LOGP(DMSC, LOGL_ERROR, "Mandatory LAYER 3 INFORMATION not present -- discarding message!\n");
+		goto fail;
+	}
+
+	/* Parse Cell ID element */
+	/* FIXME: Encapsulate this in a parser/generator function inside
+	 * libosmocore, add support for all specified cell identification
+	 * discriminators (see 3GPP ts 3.2.2.17 Cell Identifier) */
+	data_length = TLVP_LEN(&tp, GSM0808_IE_CELL_IDENTIFIER);
+	data = TLVP_VAL(&tp, GSM0808_IE_CELL_IDENTIFIER);
+	if (sizeof(lai_ci) != data_length) {
+		LOGP(DMSC, LOGL_ERROR,
+		     "Unable to parse element CELL IDENTIFIER (wrong field length) -- discarding message!\n");
+		goto fail;
+	}
+	memcpy(&lai_ci, data, sizeof(lai_ci));
+	if (lai_ci.ident != CELL_IDENT_WHOLE_GLOBAL) {
+		LOGP(DMSC, LOGL_ERROR,
+		     "Unable to parse element CELL IDENTIFIER (wrong cell identification discriminator) -- discarding message!\n");
+		goto fail;
+	}
+	if (gsm48_decode_lai(&lai_ci.lai, &mcc, &mnc, &lac) != 0) {
+		LOGP(DMSC, LOGL_ERROR,
+		     "Unable to parse element CELL IDENTIFIER (lai decoding failed) -- discarding message!\n");
+		goto fail;
+	}
+
+	/* Parse Layer 3 Information element */
+	/* FIXME: This is probably to hackish, compiler also complains "assignment discards ‘const’ qualifier..." */
+	msg->l3h = TLVP_VAL(&tp, GSM0808_IE_LAYER_3_INFORMATION);
+	msg->tail = msg->l3h + TLVP_LEN(&tp, GSM0808_IE_LAYER_3_INFORMATION);
+
+	/* Create new subscriber context */
+	conn = subscr_conn_allocate_a(a_conn_info, network, lac, scu, a_conn_info->conn_id);
+
+	/* Handover location update to the MSC code */
+	/* msc_compl_l3() takes ownership of dtap_msg
+	 * message buffer */
+	rc = msc_compl_l3(conn, msg, 0);
+	if (rc == MSC_CONN_ACCEPT) {
+		LOGP(DMSC, LOGL_NOTICE, "User has been accepted by MSC.\n");
+		return 0;
+	} else if (rc == MSC_CONN_REJECT)
+		LOGP(DMSC, LOGL_NOTICE, "User has been rejected by MSC.\n");
+	else
+		LOGP(DMSC, LOGL_NOTICE, "User has been rejected by MSC (unknown error)\n");
+
+	return -EINVAL;
+
+fail:
+	msgb_free(msg);
+	return -EINVAL;
+}
+
+/* Endpoint to handle BSSMAP classmark update */
+static int bssmap_rx_classmark_upd(struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	struct gsm_network *network = a_conn_info->network;
+	struct gsm_subscriber_connection *conn;
+	struct tlv_parsed tp;
+	const uint8_t *cm2 = NULL;
+	const uint8_t *cm3 = NULL;
+	uint8_t cm2_len = 0;
+	uint8_t cm3_len = 0;
+
+	conn = subscr_conn_lookup_a(network, a_conn_info->conn_id);
+	if (!conn)
+		goto fail;
+
+	LOGP(DMSC, LOGL_NOTICE, "BSC sends clasmark update (conn_id=%i)\n", conn->a.conn_id);
+
+	tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l3h + 1, msgb_l3len(msg) - 1, 0, 0);
+	if (!TLVP_PRESENT(&tp, GSM0808_IE_CLASSMARK_INFORMATION_T2)) {
+		LOGP(DMSC, LOGL_ERROR, "Mandatory Classmark Information Type 2 not present -- discarding message!\n");
+		goto fail;
+	}
+
+	cm2 = TLVP_VAL(&tp, GSM0808_IE_CLASSMARK_INFORMATION_T2);
+	cm2_len = TLVP_LEN(&tp, GSM0808_IE_CLASSMARK_INFORMATION_T2);
+
+	if (TLVP_PRESENT(&tp, GSM0808_IE_CLASSMARK_INFORMATION_T3)) {
+		cm3 = TLVP_VAL(&tp, GSM0808_IE_CLASSMARK_INFORMATION_T3);
+		cm3_len = TLVP_LEN(&tp, GSM0808_IE_CLASSMARK_INFORMATION_T3);
+	}
+
+	/* Inform MSC about the classmark change */
+	msc_classmark_chg(conn, cm2, cm2_len, cm3, cm3_len);
+
+	msgb_free(msg);
+	return 0;
+
+fail:
+	msgb_free(msg);
+	return -EINVAL;
+}
+
+/* Endpoint to handle BSSMAP cipher mode complete */
+static int bssmap_rx_ciph_compl(const struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info,
+				struct msgb *msg)
+{
+	/* FIXME: The field GSM0808_IE_LAYER_3_MESSAGE_CONTENTS is optional by
+	 * means of the specification. So there can be messages without L3 info.
+	 * In this case, the code will crash becrause msc_cipher_mode_compl()
+	 * is not able to deal with msg = NULL and apperently
+	 * msc_cipher_mode_compl() was never meant to be used without L3 data.
+	 * This needs to be discussed further! */
+
+	struct gsm_network *network = a_conn_info->network;
+	struct gsm_subscriber_connection *conn;
+	struct tlv_parsed tp;
+	uint8_t alg_id = 1;
+
+	conn = subscr_conn_lookup_a(network, a_conn_info->conn_id);
+	if (!conn)
+		goto fail;
+
+	LOGP(DMSC, LOGL_NOTICE, "BSC sends cipher mode complete (conn_id=%i)\n", conn->a.conn_id);
+
+	tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l3h + 1, msgb_l3len(msg) - 1, 0, 0);
+
+	if (TLVP_PRESENT(&tp, GSM0808_IE_CHOSEN_ENCR_ALG)) {
+		alg_id = TLVP_VAL(&tp, GSM0808_IE_CHOSEN_ENCR_ALG)[0] - 1;
+	}
+
+	if (TLVP_PRESENT(&tp, GSM0808_IE_LAYER_3_MESSAGE_CONTENTS)) {
+		msg->l3h = TLVP_VAL(&tp, GSM0808_IE_LAYER_3_MESSAGE_CONTENTS);
+		msg->tail = msg->l3h + TLVP_LEN(&tp, GSM0808_IE_LAYER_3_MESSAGE_CONTENTS);
+	} else {
+		msgb_free(msg);
+		msg = NULL;
+	}
+
+	/* Hand over cipher mode complete message to the MSC,
+	 * msc_cipher_mode_compl() takes ownership for msg */
+	msc_cipher_mode_compl(conn, msg, alg_id);
+
+	return 0;
+fail:
+	msgb_free(msg);
+	return -EINVAL;
+}
+
+/* Endpoint to handle BSSMAP cipher mode reject */
+static int bssmap_rx_ciph_rej(const struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	struct gsm_network *network = a_conn_info->network;
+	struct gsm_subscriber_connection *conn;
+	struct tlv_parsed tp;
+	uint8_t cause;
+
+	conn = subscr_conn_lookup_a(network, a_conn_info->conn_id);
+	if (!conn)
+		goto fail;
+
+	LOGP(DMSC, LOGL_NOTICE, "BSC sends cipher mode reject (conn_id=%i)\n", conn->a.conn_id);
+
+	tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l3h + 1, msgb_l3len(msg) - 1, 0, 0);
+	if (!TLVP_PRESENT(&tp, BSS_MAP_MSG_CIPHER_MODE_REJECT)) {
+		LOGP(DMSC, LOGL_ERROR, "Cause code is missing -- discarding message!\n");
+		goto fail;
+	}
+
+	cause = TLVP_VAL(&tp, BSS_MAP_MSG_CIPHER_MODE_REJECT)[0];
+	LOGP(DMSC, LOGL_NOTICE, "Cipher mode rejection cause: %i\n", cause);
+
+	/* FIXME: Can we do something meaningful here? e.g. report to the
+	 * msc code somehow that the cipher mode command has failed. */
+
+	msgb_free(msg);
+	return 0;
+fail:
+	msgb_free(msg);
+	return -EINVAL;
+}
+
+/* Endpoint to handle BSSMAP assignment failure */
+static int bssmap_rx_ass_fail(const struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	struct gsm_network *network = a_conn_info->network;
+	struct gsm_subscriber_connection *conn;
+	struct tlv_parsed tp;
+	uint8_t cause;
+	uint8_t *rr_cause_ptr = NULL;
+	uint8_t rr_cause;
+
+	conn = subscr_conn_lookup_a(network, a_conn_info->conn_id);
+	if (!conn)
+		goto fail;
+
+	LOGP(DMSC, LOGL_NOTICE, "BSC sends assignment failure message (conn_id=%i)\n", conn->a.conn_id);
+
+	tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l3h + 1, msgb_l3len(msg) - 1, 0, 0);
+	if (!TLVP_PRESENT(&tp, GSM0808_IE_CAUSE)) {
+		LOGP(DMSC, LOGL_ERROR, "Cause code is missing -- discarding message!\n");
+		goto fail;
+	}
+	cause = TLVP_VAL(&tp, GSM0808_IE_CAUSE)[0];
+
+	if (TLVP_PRESENT(&tp, GSM0808_IE_RR_CAUSE)) {
+		rr_cause = TLVP_VAL(&tp, GSM0808_IE_RR_CAUSE)[0];
+		rr_cause_ptr = &rr_cause;
+	}
+
+	/* FIXME: In AoIP, the Assignment failure will carry also an optional
+	 * Codec List (BSS Supported) element. It has to be discussed if we
+	 * can ignore this element. If not, The msc_assign_fail() function
+	 * call has to change. However msc_assign_fail() does nothing in the
+	 * end. So probably we can just leave it as it is. Even for AoIP */
+
+	/* Inform the MSC about the assignment failure event */
+	msc_assign_fail(conn, cause, rr_cause_ptr);
+
+	msgb_free(msg);
+	return 0;
+fail:
+	msgb_free(msg);
+	return -EINVAL;
+}
+
+/* Endpoint to handle sapi "n" reject */
+static int bssmap_rx_sapi_n_rej(const struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info,
+				struct msgb *msg)
+{
+	struct gsm_network *network = a_conn_info->network;
+	struct gsm_subscriber_connection *conn;
+	struct tlv_parsed tp;
+	uint8_t dlci;
+
+	conn = subscr_conn_lookup_a(network, a_conn_info->conn_id);
+	if (!conn)
+		goto fail;
+
+	LOGP(DMSC, LOGL_NOTICE, "BSC sends sapi \"n\" reject message (conn_id=%i)\n", conn->a.conn_id);
+
+	/* Note: The MSC code seems not to care about the cause code, but by
+	 * the specification it is mandatory, so we check its presence. See
+	 * also 3GPP TS 48.008 3.2.1.34 SAPI "n" REJECT */
+	tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l3h + 1, msgb_l3len(msg) - 1, 0, 0);
+	if (!TLVP_PRESENT(&tp, GSM0808_IE_CAUSE)) {
+		LOGP(DMSC, LOGL_ERROR, "Cause code is missing -- discarding message!\n");
+		goto fail;
+	}
+
+	tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l3h + 1, msgb_l3len(msg) - 1, 0, 0);
+	if (!TLVP_PRESENT(&tp, GSM0808_IE_DLCI)) {
+		LOGP(DMSC, LOGL_ERROR, "DLCI is missing -- discarding message!\n");
+		goto fail;
+	}
+	dlci = TLVP_VAL(&tp, GSM0808_IE_DLCI)[0];
+
+	/* Inform the MSC about the sapi "n" reject event */
+	msc_sapi_n_reject(conn, dlci);
+
+	msgb_free(msg);
+	return 0;
+fail:
+	msgb_free(msg);
+	return -EINVAL;
+}
+
+/* Endpoint to handle assignment complete */
+static int bssmap_rx_ass_compl(const struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info,
+			       struct msgb *msg)
+{
+	struct gsm_network *network = a_conn_info->network;
+	struct gsm_subscriber_connection *conn;
+	struct mgcpgw_client *mgcp;
+	struct tlv_parsed tp;
+	struct sockaddr_storage rtp_addr;
+	struct sockaddr_in *rtp_addr_in;
+	int rc;
+
+	conn = subscr_conn_lookup_a(network, a_conn_info->conn_id);
+	if (!conn)
+		goto fail;
+
+	mgcp = conn->network->mgcpgw.client;
+	OSMO_ASSERT(mgcp);
+
+	LOGP(DMSC, LOGL_NOTICE, "BSC sends assignment complete message (conn_id=%i)\n", conn->a.conn_id);
+
+	tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l3h + 1, msgb_l3len(msg) - 1, 0, 0);
+
+	if (!TLVP_PRESENT(&tp, GSM0808_IE_AOIP_TRASP_ADDR)) {
+		LOGP(DMSC, LOGL_ERROR, "AoIP transport identifier missing -- discarding message!\n");
+		goto fail;
+	}
+
+	/* Decode AoIP transport address element */
+	rc = gsm0808_dec_aoip_trasp_addr(&rtp_addr, TLVP_VAL(&tp, GSM0808_IE_AOIP_TRASP_ADDR),
+					 TLVP_LEN(&tp, GSM0808_IE_AOIP_TRASP_ADDR));
+	if (rc < 0) {
+		LOGP(DMSC, LOGL_ERROR, "Unable to decode aoip transport address.\n");
+		goto fail;
+	}
+
+	/* use address / port supplied with the AoIP
+	 * transport address element */
+	if (rtp_addr.ss_family == AF_INET) {
+		rtp_addr_in = (struct sockaddr_in *)&rtp_addr;
+		conn->rtp.port_subscr = osmo_ntohs(rtp_addr_in->sin_port);
+		/* FIXME: We also get the IP-Address of the remote (e.g. BTS)
+		 * end with the response. Currently we just ignore that address.
+		 * Instead we expect that our local MGCP gateway and the code
+		 * controlling it, magically knows the IP of the remote end. */
+	} else {
+		LOGP(DMSC, LOGL_ERROR, "Unsopported addressing scheme. (supports only IPV4)\n");
+		goto fail;
+	}
+
+	/* FIXME: Seems to be related to authentication or,
+	   encryption. Is this really in the right place? */
+	msc_rx_sec_mode_compl(conn);
+
+	msgb_free(msg);
+	return 0;
+fail:
+	msgb_free(msg);
+	return -EINVAL;
+}
+
+/* Handle incoming connection oriented BSSMAP messages */
+static int rx_bssmap(struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	if (msgb_l3len(msg) < 1) {
+		LOGP(DMSC, LOGL_NOTICE, "Error: No data received -- discarding message!\n");
+		msgb_free(msg);
+		return -1;
+	}
+
+	LOGP(DMSC, LOGL_NOTICE, "Rx MSC DT1 BSSMAP %s\n", gsm0808_bssmap_name(msg->l3h[0]));
+
+	switch (msg->l3h[0]) {
+	case BSS_MAP_MSG_CLEAR_RQST:
+		return bssmap_rx_clear_rqst(scu, a_conn_info, msg);
+		break;
+	case BSS_MAP_MSG_CLEAR_COMPLETE:
+		return bssmap_rx_clear_complete(scu, a_conn_info, msg);
+		break;
+	case BSS_MAP_MSG_COMPLETE_LAYER_3:
+		return bssmap_rx_l3_compl(scu, a_conn_info, msg);
+		break;
+	case BSS_MAP_MSG_CLASSMARK_UPDATE:
+		return bssmap_rx_classmark_upd(scu, a_conn_info, msg);
+		break;
+	case BSS_MAP_MSG_CIPHER_MODE_COMPLETE:
+		return bssmap_rx_ciph_compl(scu, a_conn_info, msg);
+		break;
+	case BSS_MAP_MSG_CIPHER_MODE_REJECT:
+		return bssmap_rx_ciph_rej(scu, a_conn_info, msg);
+		break;
+	case BSS_MAP_MSG_ASSIGMENT_FAILURE:
+		return bssmap_rx_ass_fail(scu, a_conn_info, msg);
+		break;
+	case BSS_MAP_MSG_SAPI_N_REJECT:
+		return bssmap_rx_sapi_n_rej(scu, a_conn_info, msg);
+		break;
+	case BSS_MAP_MSG_ASSIGMENT_COMPLETE:
+		return bssmap_rx_ass_compl(scu, a_conn_info, msg);
+		break;
+	default:
+		LOGP(DMSC, LOGL_ERROR, "Unimplemented msg type: %s\n", gsm0808_bssmap_name(msg->l3h[0]));
+		msgb_free(msg);
+		return -EINVAL;
+	}
+
+	return -EINVAL;
+}
+
+/* Endpoint to handle regular BSSAP DTAP messages */
+static int rx_dtap(const struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	struct gsm_network *network = a_conn_info->network;
+	struct gsm_subscriber_connection *conn;
+
+	conn = subscr_conn_lookup_a(network, a_conn_info->conn_id);
+	if (!conn) {
+		msgb_free(msg);
+		return -EINVAL;
+	}
+
+	LOGP(DMSC, LOGL_NOTICE, "BSC sends layer 3 dtap (conn_id=%i)\n", conn->a.conn_id);
+
+	/* msc_dtap expects the dtap payload in l3h */
+	msg->l3h = msg->l2h + 3;
+
+	/* Forward dtap payload into the msc,
+	 * msc_dtap() takes ownership for msg */
+	msc_dtap(conn, conn->a.conn_id, msg);
+
+	return 0;
+}
+
+/* Handle incoming connection oriented messages */
+int sccp_rx_dt(struct osmo_sccp_user *scu, const struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	OSMO_ASSERT(scu);
+	OSMO_ASSERT(a_conn_info);
+	OSMO_ASSERT(msg);
+
+	LOGP(DMSC, LOGL_NOTICE, "Rx BSC DT: %s\n", osmo_hexdump(msgb_l2(msg), msgb_l2len(msg)));
+
+	if (msgb_l2len(msg) < sizeof(struct bssmap_header)) {
+		LOGP(DMSC, LOGL_NOTICE, "The header is too short -- discarding message!\n");
+		msgb_free(msg);
+	}
+
+	switch (msg->l2h[0]) {
+	case BSSAP_MSG_BSS_MANAGEMENT:
+		msg->l3h = &msg->l2h[sizeof(struct bssmap_header)];
+		return rx_bssmap(scu, a_conn_info, msg);
+		break;
+	case BSSAP_MSG_DTAP:
+		return rx_dtap(scu, a_conn_info, msg);
+		break;
+	default:
+		LOGP(DMSC, LOGL_ERROR, "Unimplemented BSSAP msg type: %s\n", gsm0808_bssap_name(msg->l2h[0]));
+		msgb_free(msg);
+		return -EINVAL;
+	}
+
+	return -EINVAL;
+}