diff --git a/src/libmsc/ran_msg_a.c b/src/libmsc/ran_msg_a.c
new file mode 100644
index 0000000..2e498a2
--- /dev/null
+++ b/src/libmsc/ran_msg_a.c
@@ -0,0 +1,1284 @@
+/* BSSAP/BSSMAP encoding and decoding for MSC */
+/*
+ * (C) 2019 by sysmocom - s.m.f.c. GmbH <info@sysmocom.de>
+ * All Rights Reserved
+ *
+ * Author: Neels Hofmeyr
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <osmocom/core/byteswap.h>
+
+#include <osmocom/crypt/auth.h>
+
+#include <osmocom/gsm/tlv.h>
+#include <osmocom/gsm/gsm0808.h>
+#include <osmocom/gsm/mncc.h>
+#include <osmocom/gsm/gsm48.h>
+
+#include <osmocom/msc/debug.h>
+#include <osmocom/msc/ran_msg_a.h>
+#include <osmocom/msc/sccp_ran.h>
+
+#define LOG_RAN_A_DEC(RAN_DEC, level, fmt, args...) \
+	LOG_RAN_DEC(RAN_DEC, DBSSAP, level, "BSSMAP: " fmt, ## args)
+
+/* Assumes presence of struct ran_dec *ran_dec and ran_dec_msg.msg_name (set) in the local scope. */
+#define LOG_RAN_A_DEC_MSG(level, fmt, args...) \
+	LOG_RAN_DEC(ran_dec, DBSSAP, level, "%s: " fmt, ran_dec_msg.msg_name, ## args)
+
+#define LOG_RAN_A_ENC(FI, level, fmt, args...) \
+	LOG_RAN_ENC(FI, DBSSAP, level, "BSSMAP: " fmt, ## args)
+
+static int ran_a_decode_l3_compl(struct ran_dec *ran_dec, struct msgb *msg, struct tlv_parsed *tp)
+{
+	struct gsm0808_cell_id_list2 cil;
+	struct gsm0808_cell_id cell_id;
+	struct tlv_p_entry *ie_cell_id = TLVP_GET(tp, GSM0808_IE_CELL_IDENTIFIER);
+	struct tlv_p_entry *ie_l3_info = TLVP_GET(tp, GSM0808_IE_LAYER_3_INFORMATION);
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_COMPL_L3,
+		.msg_name = "BSSMAP Complete Layer 3",
+		.compl_l3 = {
+			.cell_id = &cell_id,
+			.msg = msg,
+		},
+	};
+	int rc;
+
+	if (!ie_cell_id) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Mandatory CELL IDENTIFIER not present, discarding message\n");
+		return -EINVAL;
+	}
+	if (!ie_l3_info) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Mandatory LAYER 3 INFORMATION not present, discarding message\n");
+		return -EINVAL;
+	}
+
+	/* Parse Cell ID element -- this should yield a cell identifier "list" with 1 element. */
+
+	rc = gsm0808_dec_cell_id_list2(&cil, ie_cell_id->val, ie_cell_id->len);
+	if (rc < 0) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Decoding CELL IDENTIFIER gave rc=%d\n", rc);
+		return -EINVAL;
+	}
+	if (cil.id_list_len != 1) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Unable to parse element CELL IDENTIFIER, discarding message\n");
+		return -EINVAL;
+	}
+
+	/* Sanity check the Cell Identity */
+	switch (cil.id_discr) {
+	case CELL_IDENT_WHOLE_GLOBAL:
+	case CELL_IDENT_LAI_AND_LAC:
+	case CELL_IDENT_LAC_AND_CI:
+	case CELL_IDENT_LAC:
+		break;
+
+	case CELL_IDENT_CI:
+	case CELL_IDENT_NO_CELL:
+	case CELL_IDENT_BSS:
+	default:
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "CELL IDENTIFIER does not specify a LAC, discarding message: %s\n",
+				 gsm0808_cell_id_list_name(&cil));
+		return -EINVAL;
+	}
+
+	cell_id = (struct gsm0808_cell_id){
+		.id_discr = cil.id_discr,
+		.id = cil.id_list[0],
+	};
+
+	/* Parse Layer 3 Information element */
+	msg->l3h = (uint8_t*)ie_l3_info->val;
+	msgb_l3trim(msg, ie_l3_info->len);
+
+	if (msgb_l3len(msg) < sizeof(struct gsm48_hdr)) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "too short L3 info (%d), discarding message\n", msgb_l3len(msg));
+		return -ENODATA;
+	}
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_clear_request(struct ran_dec *ran_dec, struct msgb *msg, struct tlv_parsed *tp)
+{
+	struct tlv_p_entry *ie_cause = TLVP_GET(tp, GSM0808_IE_CAUSE);
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_CLEAR_REQUEST,
+		.msg_name = "BSSMAP Clear Request",
+	};
+
+	if (!ie_cause) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Cause code is missing, using GSM0808_CAUSE_EQUIPMENT_FAILURE\n");
+		ran_dec_msg.clear_request.bssap_cause = GSM0808_CAUSE_EQUIPMENT_FAILURE;
+	} else {
+		ran_dec_msg.clear_request.bssap_cause = ie_cause->val[0];
+	}
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_clear_complete(struct ran_dec *ran_dec, struct msgb *msg, struct tlv_parsed *tp)
+{
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_CLEAR_COMPLETE,
+		.msg_name = "BSSMAP Clear Complete",
+	};
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_classmark_update(struct ran_dec *ran_dec, struct msgb *msg, struct tlv_parsed *tp)
+{
+	struct tlv_p_entry *ie_cm2 = TLVP_GET(tp, GSM0808_IE_CLASSMARK_INFORMATION_T2);
+	struct tlv_p_entry *ie_cm3 = TLVP_GET(tp, GSM0808_IE_CLASSMARK_INFORMATION_T3);
+	struct osmo_gsm48_classmark cm = {};
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_CLASSMARK_UPDATE,
+		.msg_name = "BSSMAP Classmark Update",
+		.classmark_update = {
+			.classmark = &cm,
+		},
+	};
+
+	if (!ie_cm2) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "mandatory Classmark Information Type 2 not present, discarding message\n");
+		return -EINVAL;
+	}
+
+	cm.classmark2_len = OSMO_MIN(sizeof(cm.classmark2), ie_cm2->len);
+	memcpy(&cm.classmark2, ie_cm2->val, cm.classmark2_len);
+
+	if (ie_cm3) {
+		cm.classmark3_len = OSMO_MIN(sizeof(cm.classmark3), ie_cm3->len);
+		memcpy(&cm.classmark3, ie_cm3->val, cm.classmark3_len);
+	}
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_cipher_mode_complete(struct ran_dec *ran_dec, struct msgb *msg, struct tlv_parsed *tp)
+{
+	struct tlv_p_entry *ie_chosen_encr_alg = TLVP_GET(tp, GSM0808_IE_CHOSEN_ENCR_ALG);
+	struct tlv_p_entry *ie_l3_msg = TLVP_GET(tp, GSM0808_IE_LAYER_3_MESSAGE_CONTENTS);
+	int rc;
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_CIPHER_MODE_COMPLETE,
+		.msg_name = "BSSMAP Ciphering Mode Complete",
+	};
+
+	if (ie_chosen_encr_alg) {
+		uint8_t ie_val = ie_chosen_encr_alg->val[0];
+		/* 3GPP TS 48.008 3.2.2.44 Chosen Encryption Algorithm encodes as 1 = no encryption, 2 = A5/1, 4 = A5/3.
+		 * Internally we handle without this weird off-by-one. */
+		if (ie_val < 1 || ie_val > 8)
+			LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Unsupported value for 3.2.2.44 Chosen Encryption Algorithm: %u\n",
+					 ie_val);
+		else
+			ran_dec_msg.cipher_mode_complete.alg_id = ie_chosen_encr_alg->val[0];
+	}
+
+	rc = ran_decoded(ran_dec, &ran_dec_msg);
+
+	if (ie_l3_msg) {
+		msg->l3h = (uint8_t*)ie_l3_msg->val;
+		msgb_l3trim(msg, ie_l3_msg->len);
+		ran_dec_msg = (struct ran_msg){
+			.msg_type = RAN_MSG_DTAP,
+			.msg_name = "BSSMAP Ciphering Mode Complete (L3 Message Contents)",
+			.dtap = msg,
+		};
+		ran_decoded(ran_dec, &ran_dec_msg);
+	}
+
+	return rc;
+}
+
+static int ran_a_decode_cipher_mode_reject(struct ran_dec *ran_dec, struct msgb *msg, struct tlv_parsed *tp)
+{
+	int rc;
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_CIPHER_MODE_REJECT,
+		.msg_name = "BSSMAP Ciphering Mode Reject",
+	};
+
+	rc = gsm0808_get_cipher_reject_cause(tp);
+	if (rc < 0) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "failed to extract Cause\n");
+		ran_dec_msg.cipher_mode_reject.bssap_cause = GSM0808_CAUSE_EQUIPMENT_FAILURE;
+	} else {
+		ran_dec_msg.cipher_mode_reject.bssap_cause = (enum gsm0808_cause)rc;
+	}
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+enum mgcp_codecs ran_a_mgcp_codec_from_sc(const struct gsm0808_speech_codec *sc)
+{
+	switch (sc->type) {
+	case GSM0808_SCT_FR1:
+		return CODEC_GSM_8000_1;
+		break;
+	case GSM0808_SCT_FR2:
+		return CODEC_GSMEFR_8000_1;
+		break;
+	case GSM0808_SCT_FR3:
+		return CODEC_AMR_8000_1;
+		break;
+	case GSM0808_SCT_FR4:
+		return CODEC_AMRWB_16000_1;
+		break;
+	case GSM0808_SCT_FR5:
+		return CODEC_AMRWB_16000_1;
+		break;
+	case GSM0808_SCT_HR1:
+		return CODEC_GSMHR_8000_1;
+		break;
+	case GSM0808_SCT_HR3:
+		return CODEC_AMR_8000_1;
+		break;
+	case GSM0808_SCT_HR4:
+		return CODEC_AMRWB_16000_1;
+		break;
+	case GSM0808_SCT_HR6:
+		return CODEC_AMRWB_16000_1;
+		break;
+	default:
+		return CODEC_PCMU_8000_1;
+		break;
+	}
+}
+
+static int ran_a_decode_assignment_complete(struct ran_dec *ran_dec, struct msgb *msg, struct tlv_parsed *tp)
+{
+	struct tlv_p_entry *ie_aoip_transp_addr = TLVP_GET(tp, GSM0808_IE_AOIP_TRASP_ADDR);
+	struct tlv_p_entry *ie_speech_codec = TLVP_GET(tp, GSM0808_IE_SPEECH_CODEC);
+	struct sockaddr_storage rtp_addr;
+	struct sockaddr_in *rtp_addr_in;
+	struct gsm0808_speech_codec sc;
+	int rc;
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_ASSIGNMENT_COMPLETE,
+		.msg_name = "BSSMAP Assignment Complete",
+	};
+
+	if (ie_aoip_transp_addr) {
+		/* Decode AoIP transport address element */
+		rc = gsm0808_dec_aoip_trasp_addr(&rtp_addr, ie_aoip_transp_addr->val, ie_aoip_transp_addr->len);
+		if (rc < 0) {
+			LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Unable to decode AoIP Transport Layer Address\n");
+			return -EINVAL;
+		}
+
+		rtp_addr_in = (struct sockaddr_in*)&rtp_addr;
+
+		if (rtp_addr.ss_family != AF_INET) {
+			LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Assignment Complete: IE AoIP Transport Address:"
+				 " unsupported addressing scheme (only IPV4 supported)\n");
+			return -EINVAL;
+		}
+
+		if (osmo_sockaddr_str_from_sockaddr_in(&ran_dec_msg.assignment_complete.remote_rtp, rtp_addr_in)) {
+			LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Assignment Complete: unable to decode remote RTP IP address\n");
+			return -EINVAL;
+		}
+	}
+
+	if (ie_speech_codec) {
+		/* Decode Speech Codec (Chosen) element */
+		rc = gsm0808_dec_speech_codec(&sc, ie_speech_codec->val, ie_speech_codec->len);
+		if (rc < 0) {
+			LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Assignment Complete: unable to decode IE Speech Codec (Chosen)"
+					  " (rc=%d).\n", rc);
+			return -EINVAL;
+		}
+		ran_dec_msg.assignment_complete.codec_present = true;
+		ran_dec_msg.assignment_complete.codec = ran_a_mgcp_codec_from_sc(&sc);
+	}
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_assignment_failure(struct ran_dec *ran_dec, struct msgb *msg, struct tlv_parsed *tp)
+{
+	struct tlv_p_entry *ie_cause = TLVP_GET(tp, GSM0808_IE_CAUSE);
+	struct tlv_p_entry *ie_rr_cause = TLVP_GET(tp, GSM0808_IE_RR_CAUSE);
+	struct tlv_p_entry *ie_speech_codec_list = TLVP_GET(tp, GSM0808_IE_SPEECH_CODEC_LIST);
+	struct gsm0808_speech_codec_list scl;
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_ASSIGNMENT_FAILURE,
+		.msg_name = "BSSMAP Assignment Failure",
+		.assignment_failure = {
+			.bssap_cause = GSM0808_CAUSE_EQUIPMENT_FAILURE,
+			.rr_cause = GSM48_RR_CAUSE_ABNORMAL_UNSPEC,
+		},
+	};
+
+	if (ie_cause)
+		ran_dec_msg.assignment_failure.bssap_cause = ie_cause->val[0];
+	if (ie_rr_cause)
+		ran_dec_msg.assignment_failure.rr_cause = ie_rr_cause->val[0];
+
+	if (ie_speech_codec_list
+	    && gsm0808_dec_speech_codec_list(&scl, ie_speech_codec_list->val, ie_speech_codec_list->len) == 0)
+		ran_dec_msg.assignment_failure.scl_bss_supported = &scl;
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_sapi_n_reject(struct ran_dec *ran_dec, struct msgb *msg, struct tlv_parsed *tp)
+{
+	struct tlv_p_entry *ie_cause = TLVP_GET(tp, GSM0808_IE_CAUSE);
+	struct tlv_p_entry *ie_dlci = TLVP_GET(tp, GSM0808_IE_DLCI);
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_SAPI_N_REJECT,
+		.msg_name = "BSSMAP SAPI-N Reject",
+	};
+
+	/* 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 */
+	if (!ie_cause) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "SAPI-N Reject: cause code IE is missing, discarding message\n");
+		return -EINVAL;
+	}
+	ran_dec_msg.sapi_n_reject.bssap_cause = ie_cause->val[0];
+
+	if (!ie_dlci) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "SAPI-N Reject: DLCI IE is missing, discarding message\n");
+		return -EINVAL;
+	}
+	ran_dec_msg.sapi_n_reject.dlci = ie_dlci->val[0];
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_lcls_notification(struct ran_dec *ran_dec, const struct msgb *msg, const struct tlv_parsed *tp)
+{
+	const struct tlv_p_entry *ie_lcls_bss_status = TLVP_GET(tp, GSM0808_IE_LCLS_BSS_STATUS);
+	const struct tlv_p_entry *ie_lcls_break_req = TLVP_GET(tp, GSM0808_IE_LCLS_BREAK_REQ);
+	struct ran_msg ran_dec_msg;
+
+	/* Either §3.2.2.119 LCLS-BSS-Status or §3.2.2.120 LCLS-Break-Request shall be present */
+	if ((!ie_lcls_bss_status && !ie_lcls_break_req)
+	    || (ie_lcls_bss_status && ie_lcls_break_req)) {
+		LOG_RAN_A_DEC(ran_dec, LOGL_ERROR, "Ignoring broken LCLS Notification message\n");
+		return -EINVAL;
+	}
+
+	if (ie_lcls_bss_status) {
+		ran_dec_msg = (struct ran_msg){
+			.msg_type = RAN_MSG_LCLS_STATUS,
+			.msg_name = "BSSMAP LCLS Notification (LCLS Status)",
+			.lcls_status = {
+				.status = ie_lcls_bss_status->len ?
+					ie_lcls_bss_status->val[0] : GSM0808_LCLS_STS_NA,
+			},
+		};
+		return ran_decoded(ran_dec, &ran_dec_msg);
+	}
+
+	if (ie_lcls_break_req) {
+		ran_dec_msg = (struct ran_msg){
+			.msg_type = RAN_MSG_LCLS_BREAK_REQ,
+			.msg_name = "BSSMAP LCLS Notification (LCLS Break Req)",
+			.lcls_break_req = {
+				.todo = 23,
+			},
+		};
+		return ran_decoded(ran_dec, &ran_dec_msg);
+	}
+
+	return -EINVAL;
+}
+
+static int ran_a_decode_handover_required(struct ran_dec *ran_dec, const struct msgb *msg, const struct tlv_parsed *tp)
+{
+	const struct tlv_p_entry *ie_cause = TLVP_GET(tp, GSM0808_IE_CAUSE);
+	const struct tlv_p_entry *ie_cil = TLVP_GET(tp, GSM0808_IE_CELL_IDENTIFIER_LIST);
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_HANDOVER_REQUIRED,
+		.msg_name = "BSSMAP Handover Required",
+	};
+	/* On decoding failures, dispatch an invalid RAN_MSG_HANDOVER_REQUIRED so msc_a can pass down a
+	 * BSS_MAP_MSG_HANDOVER_REQUIRED_REJECT	message. */
+
+	if (ie_cause)
+		ran_dec_msg.handover_required.cause = ie_cause->val[0];
+	else
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Cause IE missing\n");
+
+	if (!ie_cil
+	    || gsm0808_dec_cell_id_list2(&ran_dec_msg.handover_required.cil, ie_cil->val, ie_cil->len) <= 0) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "No or invalid Cell Identifier List IE\n");
+		ran_dec_msg.handover_required.cil = (struct gsm0808_cell_id_list2){};
+	}
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static uint8_t a5_encryption_mask_from_gsm0808_chosen_enc_alg(enum gsm0808_chosen_enc_alg val)
+{
+	return 1 << val;
+}
+
+static int ran_a_decode_handover_request(struct ran_dec *ran_dec, const struct msgb *msg, const struct tlv_parsed *tp)
+{
+	struct osmo_gsm48_classmark classmark = {};
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_HANDOVER_REQUEST,
+		.msg_name = "BSSMAP Handover Request",
+		.handover_request = {
+			.classmark = &classmark,
+		},
+	};
+	struct ran_handover_request *r = &ran_dec_msg.handover_request;
+
+	const struct tlv_p_entry *ie_channel_type = TLVP_GET(tp, GSM0808_IE_CHANNEL_TYPE);
+	const struct tlv_p_entry *ie_encryption_information = TLVP_GET(tp, GSM0808_IE_ENCRYPTION_INFORMATION);
+	const struct tlv_p_entry *ie_classmark1 = TLVP_GET(tp, GSM0808_IE_CLASSMARK_INFORMATION_TYPE_1);
+	const struct tlv_p_entry *ie_classmark2 = TLVP_GET(tp, GSM0808_IE_CLASSMARK_INFORMATION_T2);
+	const struct tlv_p_entry *ie_cell_id_serving = TLVP_GET(&tp[0], GSM0808_IE_CELL_IDENTIFIER);
+	const struct tlv_p_entry *ie_cell_id_target = TLVP_GET(&tp[1], GSM0808_IE_CELL_IDENTIFIER);
+	const struct tlv_p_entry *ie_cause = TLVP_GET(tp, GSM0808_IE_CAUSE);
+	const struct tlv_p_entry *ie_classmark3 = TLVP_GET(tp, GSM0808_IE_CLASSMARK_INFORMATION_T3);
+	const struct tlv_p_entry *ie_current_channel_type_1 = TLVP_GET(tp, GSM0808_IE_CURRENT_CHANNEL_TYPE_1);
+	const struct tlv_p_entry *ie_speech_version_used = TLVP_GET(tp, GSM0808_IE_SPEECH_VERSION);
+	const struct tlv_p_entry *ie_chosen_encr_alg_serving = TLVP_GET(tp, GSM0808_IE_CHOSEN_ENCR_ALG);
+	const struct tlv_p_entry *ie_old_bss_to_new_bss_info = TLVP_GET(tp, GSM0808_IE_OLD_BSS_TO_NEW_BSS_INFORMATION);
+	const struct tlv_p_entry *ie_imsi = TLVP_GET(tp, GSM0808_IE_IMSI);
+	const struct tlv_p_entry *ie_aoip_transp_addr = TLVP_GET(tp, GSM0808_IE_AOIP_TRASP_ADDR);
+	const struct tlv_p_entry *ie_codec_list_msc_preferred = TLVP_GET(tp, GSM0808_IE_SPEECH_CODEC_LIST);
+	const struct tlv_p_entry *ie_call_id = TLVP_GET(tp, GSM0808_IE_CALL_ID);
+	const struct tlv_p_entry *ie_global_call_ref = TLVP_GET(tp, GSM0808_IE_GLOBAL_CALL_REF);
+
+	struct gsm0808_channel_type channel_type;
+	struct gsm0808_encrypt_info encr_info;
+	struct gsm0808_speech_codec_list scl;
+	struct geran_encr geran_encr = {};
+	char imsi[OSMO_IMSI_BUF_SIZE];
+	struct osmo_sockaddr_str rtp_ran_local;
+
+	if (!ie_channel_type) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Mandatory IE missing: Channel Type\n");
+		return -EINVAL;
+	}
+	if (gsm0808_dec_channel_type(&channel_type, ie_channel_type->val, ie_channel_type->len) <= 0) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Failed to decode Channel Type IE\n");
+		return -EINVAL;
+	}
+	r->geran.channel_type = &channel_type;
+
+	if (ie_encryption_information) {
+		int i;
+		if (gsm0808_dec_encrypt_info(&encr_info, ie_encryption_information->val, ie_encryption_information->len)
+		    <= 0) {
+			LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Failed to decode Encryption Informaiton IE\n");
+			return -EINVAL;
+		}
+
+		for (i = 0; i < encr_info.perm_algo_len; i++) {
+			r->geran.a5_encryption_mask |=
+				a5_encryption_mask_from_gsm0808_chosen_enc_alg(encr_info.perm_algo[i]);
+		}
+
+		if (encr_info.key_len > sizeof(geran_encr.key)) {
+			LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Failed to decode Encryption Informaiton IE:"
+					  " encryption key is too long: %u\n", geran_encr.key_len);
+			return -EINVAL;
+		}
+
+		if (encr_info.key_len) {
+			memcpy(geran_encr.key, encr_info.key, encr_info.key_len);
+			geran_encr.key_len = encr_info.key_len;
+		}
+
+		r->geran.chosen_encryption = &geran_encr;
+	}
+
+	if (!ie_classmark1 && !ie_classmark2) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Mandatory IE missing: either Classmark Information 1"
+				  " or Classmark Information 2 must be included\n");
+		return -EINVAL;
+	}
+
+	if (ie_classmark1) {
+		if (ie_classmark1->len != sizeof(classmark.classmark1)) {
+			LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Invalid size for Classmark 1: %u, expected %zu\n",
+					  ie_classmark1->len, sizeof(classmark.classmark1));
+			return -EINVAL;
+		}
+		memcpy((uint8_t*)&classmark.classmark1, ie_classmark1->val, ie_classmark1->len);
+		classmark.classmark1_set = true;
+	}
+
+	if (ie_classmark2) {
+		uint8_t len = OSMO_MIN(ie_classmark2->len, sizeof(classmark.classmark2));
+		memcpy((uint8_t*)&classmark.classmark2, ie_classmark2->val, len);
+		classmark.classmark2_len = len;
+	}
+
+	if (!ie_cell_id_serving) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Mandatory IE missing: Cell Identifier (Serving)\n");
+		return -EINVAL;
+	}
+	if (gsm0808_dec_cell_id(&r->cell_id_serving, ie_cell_id_serving->val,
+				ie_cell_id_serving->len) <= 0) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Failed to decode Cell Identifier (Serving) IE\n");
+		return -EINVAL;
+	}
+
+	if (!ie_cell_id_target) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Mandatory IE missing: Cell Identifier (Target)\n");
+		return -EINVAL;
+	}
+	if (gsm0808_dec_cell_id(&r->cell_id_target, ie_cell_id_target->val,
+				ie_cell_id_target->len) <= 0) {
+		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "Failed to decode Cell Identifier (Target) IE\n");
+		return -EINVAL;
+	}
+
+	if (ie_cause)
+		r->bssap_cause = ie_cause->val[0];
+
+	if (ie_classmark3) {
+		uint8_t len = OSMO_MIN(ie_classmark3->len, sizeof(classmark.classmark3));
+		memcpy(classmark.classmark3, ie_classmark3->val, len);
+		classmark.classmark3_len = len;
+	}
+
+	if (ie_current_channel_type_1) {
+		r->current_channel_type_1 = ie_current_channel_type_1->val[0];
+		r->current_channel_type_1_present = true;
+	}
+
+	if (ie_speech_version_used) {
+		r->speech_version_used = ie_speech_version_used->val[0];
+	}
+
+	if (ie_chosen_encr_alg_serving && ie_chosen_encr_alg_serving->len) {
+		geran_encr.alg_id = ie_chosen_encr_alg_serving->val[0];
+		r->geran.chosen_encryption = &geran_encr;
+	}
+
+	if (ie_old_bss_to_new_bss_info) {
+		r->old_bss_to_new_bss_info_raw = ie_old_bss_to_new_bss_info->val;
+		r->old_bss_to_new_bss_info_raw_len = ie_old_bss_to_new_bss_info->len;
+	}
+
+	if (ie_imsi) {
+		gsm48_mi_to_string(imsi, sizeof(imsi), ie_imsi->val, ie_imsi->len);
+		r->imsi = imsi;
+	}
+
+	if (ie_aoip_transp_addr) {
+		do {
+			struct sockaddr_storage rtp_addr;
+			if (gsm0808_dec_aoip_trasp_addr(&rtp_addr, ie_aoip_transp_addr->val, ie_aoip_transp_addr->len) < 0) {
+				LOG_RAN_A_DEC_MSG(LOGL_ERROR, "unable to decode AoIP transport address\n");
+				break;
+			}
+			if (rtp_addr.ss_family != AF_INET) {
+				LOG_RAN_A_DEC_MSG(LOGL_ERROR, "IE AoIP Transport Address:"
+						 " unsupported addressing scheme (only IPV4 supported)\n");
+				break;
+			}
+			if (osmo_sockaddr_str_from_sockaddr_in(&rtp_ran_local, (struct sockaddr_in*)&rtp_addr)) {
+				LOG_RAN_A_DEC_MSG(LOGL_ERROR, "unable to decode remote RTP IP address\n");
+				break;
+			}
+			r->rtp_ran_local = &rtp_ran_local;
+		} while(0);
+	}
+
+	if (ie_codec_list_msc_preferred
+	    && gsm0808_dec_speech_codec_list(&scl, ie_codec_list_msc_preferred->val,
+					     ie_codec_list_msc_preferred->len) == 0)
+		r->codec_list_msc_preferred = &scl;
+
+	if (ie_call_id && ie_call_id->len == 4) {
+		r->call_id = osmo_load32le(ie_call_id->val);
+		r->call_id_present = true;
+	}
+
+	if (ie_global_call_ref) {
+		r->global_call_reference = ie_global_call_ref->val;
+		r->global_call_reference_len = ie_global_call_ref->len;
+	}
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_handover_request_ack(struct ran_dec *ran_dec, const struct msgb *msg, const struct tlv_parsed *tp)
+{
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_HANDOVER_REQUEST_ACK,
+		.msg_name = "BSSMAP Handover Request Acknowledge",
+	};
+	const struct tlv_p_entry *ie_l3_info = TLVP_GET(tp, GSM0808_IE_LAYER_3_INFORMATION);
+	const struct tlv_p_entry *ie_aoip_transp_addr = TLVP_GET(tp, GSM0808_IE_AOIP_TRASP_ADDR);
+	const struct tlv_p_entry *ie_speech_codec = TLVP_GET(tp, GSM0808_IE_SPEECH_CODEC);
+	const struct tlv_p_entry *ie_chosen_channel = TLVP_GET(tp, GSM0808_IE_CHOSEN_CHANNEL);
+	const struct tlv_p_entry *ie_chosen_encr_alg = TLVP_GET(tp, GSM0808_IE_CHOSEN_ENCR_ALG);
+	const struct tlv_p_entry *ie_chosen_speech_version = TLVP_GET(tp, GSM0808_IE_SPEECH_VERSION);
+
+	/* On missing mandatory IEs, dispatch an invalid RAN_MSG_HANDOVER_REQUEST_ACK so msc_a can act on the failure. */
+
+	if (ie_l3_info) {
+		ran_dec_msg.handover_request_ack.rr_ho_command = ie_l3_info->val;
+		ran_dec_msg.handover_request_ack.rr_ho_command_len = ie_l3_info->len;
+	}
+
+	if (ie_chosen_channel) {
+		ran_dec_msg.handover_request_ack.chosen_channel_present = true;
+		ran_dec_msg.handover_request_ack.chosen_channel = *ie_chosen_channel->val;
+	}
+
+	if (ie_chosen_encr_alg) {
+		ran_dec_msg.handover_request_ack.chosen_encr_alg = *ie_chosen_encr_alg->val;
+		if (ran_dec_msg.handover_request_ack.chosen_encr_alg < 1
+		    || ran_dec_msg.handover_request_ack.chosen_encr_alg > 8) {
+			LOG_RAN_A_DEC_MSG(LOGL_ERROR, "invalid Chosen Encryption Algorithm: %u\n",
+					 ran_dec_msg.handover_request_ack.chosen_encr_alg);
+		}
+	}
+
+	if (ie_chosen_speech_version) {
+		struct gsm0808_speech_codec sc;
+		ran_dec_msg.handover_request_ack.chosen_speech_version = ie_chosen_speech_version->val[0];
+
+		/* the codec may be extrapolated from this Speech Version or below from Speech Codec */
+		gsm0808_speech_codec_from_chan_type(&sc, ran_dec_msg.handover_request_ack.chosen_speech_version);
+		ran_dec_msg.handover_request_ack.codec_present = true;
+		ran_dec_msg.handover_request_ack.codec = ran_a_mgcp_codec_from_sc(&sc);
+	}
+
+	if (ie_aoip_transp_addr) {
+		do {
+			struct sockaddr_storage rtp_addr;
+			if (gsm0808_dec_aoip_trasp_addr(&rtp_addr, ie_aoip_transp_addr->val, ie_aoip_transp_addr->len) < 0) {
+				LOG_RAN_A_DEC_MSG(LOGL_ERROR, "unable to decode AoIP transport address\n");
+				break;
+			}
+			if (rtp_addr.ss_family != AF_INET) {
+				LOG_RAN_A_DEC_MSG(LOGL_ERROR, "IE AoIP Transport Address:"
+						 " unsupported addressing scheme (only IPV4 supported)\n");
+				break;
+			}
+			if (osmo_sockaddr_str_from_sockaddr_in(&ran_dec_msg.handover_request_ack.remote_rtp,
+							  (struct sockaddr_in*)&rtp_addr)) {
+				LOG_RAN_A_DEC_MSG(LOGL_ERROR, "unable to decode remote RTP IP address\n");
+				ran_dec_msg.handover_request_ack.remote_rtp = (struct osmo_sockaddr_str){};
+				break;
+			}
+		} while(0);
+	}
+
+	if (ie_speech_codec) {
+		struct gsm0808_speech_codec sc;
+		if (gsm0808_dec_speech_codec(&sc, ie_speech_codec->val, ie_speech_codec->len) < 0)
+			LOG_RAN_A_DEC_MSG(LOGL_ERROR, "unable to decode IE Speech Codec (Chosen)\n");
+		else {
+			/* the codec may be extrapolated from above Speech Version or from this Speech Codec */
+			ran_dec_msg.handover_request_ack.codec_present = true;
+			ran_dec_msg.handover_request_ack.codec = ran_a_mgcp_codec_from_sc(&sc);
+		}
+	}
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_handover_detect(struct ran_dec *ran_dec, const struct msgb *msg, const struct tlv_parsed *tp)
+{
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_HANDOVER_DETECT,
+		.msg_name = "BSSMAP Handover Detect",
+	};
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_handover_succeeded(struct ran_dec *ran_dec, const struct msgb *msg, const struct tlv_parsed *tp)
+{
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_HANDOVER_SUCCEEDED,
+		.msg_name = "BSSMAP Handover Succeeded",
+	};
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_handover_complete(struct ran_dec *ran_dec, const struct msgb *msg, const struct tlv_parsed *tp)
+{
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_HANDOVER_COMPLETE,
+		.msg_name = "BSSMAP Handover Complete",
+	};
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_handover_failure(struct ran_dec *ran_dec, const struct msgb *msg, const struct tlv_parsed *tp)
+{
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_HANDOVER_FAILURE,
+		.msg_name = "BSSMAP Handover Failure",
+	};
+
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+static int ran_a_decode_bssmap(struct ran_dec *ran_dec, struct msgb *bssmap)
+{
+	struct tlv_parsed tp[2];
+	int rc;
+	struct bssmap_header *h = msgb_l2(bssmap);
+	uint8_t msg_type;
+	bssmap->l3h = bssmap->l2h + sizeof(*h);
+
+	if (msgb_l3len(bssmap) < 1) {
+		LOG_RAN_A_DEC(ran_dec, LOGL_ERROR, "No data received, discarding message\n");
+		return -1;
+	}
+
+	if (msgb_l3len(bssmap) < h->length) {
+		LOG_RAN_A_DEC(ran_dec, LOGL_ERROR, "BSSMAP data truncated, discarding message\n");
+		return -1;
+	}
+
+	if (msgb_l3len(bssmap) > h->length) {
+		LOG_RAN_A_DEC(ran_dec, LOGL_NOTICE, "There are %u extra bytes after the BSSMAP data, truncating\n",
+			     msgb_l3len(bssmap) - h->length);
+		msgb_l3trim(bssmap, h->length);
+	}
+
+	/* h->type == BSSAP_MSG_BSS_MANAGEMENT; h->length is the data length,
+	 * which starts with the MAP msg_type, followed by IEs. */
+	msg_type = bssmap->l3h[0];
+	rc = osmo_bssap_tlv_parse2(tp, ARRAY_SIZE(tp), bssmap->l3h + 1, h->length - 1);
+	if (rc < 0) {
+		LOG_RAN_A_DEC(ran_dec, LOGL_ERROR, "Failed parsing TLV, discarding message\n");
+		return -EINVAL;
+	}
+
+	LOG_RAN_A_DEC(ran_dec, LOGL_DEBUG, "Rx BSSMAP DT1 %s\n", gsm0808_bssmap_name(msg_type));
+
+	switch (msg_type) {
+	case BSS_MAP_MSG_COMPLETE_LAYER_3:
+		return ran_a_decode_l3_compl(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_CLEAR_RQST:
+		return ran_a_decode_clear_request(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_CLEAR_COMPLETE:
+		return ran_a_decode_clear_complete(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_CLASSMARK_UPDATE:
+		return ran_a_decode_classmark_update(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_CIPHER_MODE_COMPLETE:
+		return ran_a_decode_cipher_mode_complete(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_CIPHER_MODE_REJECT:
+		return ran_a_decode_cipher_mode_reject(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_ASSIGMENT_COMPLETE:
+		rc = ran_a_decode_assignment_complete(ran_dec, bssmap, tp);
+		if (rc < 0) {
+			struct ran_msg ran_dec_msg = {
+				.msg_type = RAN_MSG_ASSIGNMENT_FAILURE,
+				.msg_name = "BSSMAP Assignment Complete but failed to decode",
+				.clear_request = {
+					.bssap_cause = GSM0808_CAUSE_EQUIPMENT_FAILURE,
+				},
+			};
+			ran_decoded(ran_dec, &ran_dec_msg);
+		}
+		return rc;
+	case BSS_MAP_MSG_ASSIGMENT_FAILURE:
+		return ran_a_decode_assignment_failure(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_SAPI_N_REJECT:
+		return ran_a_decode_sapi_n_reject(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_LCLS_NOTIFICATION:
+		return ran_a_decode_lcls_notification(ran_dec, bssmap, tp);
+
+	/* From current RAN peer, the Handover origin: */
+	case BSS_MAP_MSG_HANDOVER_REQUIRED:
+		return ran_a_decode_handover_required(ran_dec, bssmap, tp);
+
+	/* From current MSC to remote handover target MSC */
+	case BSS_MAP_MSG_HANDOVER_RQST:
+		return ran_a_decode_handover_request(ran_dec, bssmap, tp);
+
+	/* From potential new RAN peer, the Handover target: */
+	case BSS_MAP_MSG_HANDOVER_RQST_ACKNOWLEDGE:
+		return ran_a_decode_handover_request_ack(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_HANDOVER_DETECT:
+		return ran_a_decode_handover_detect(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_HANDOVER_SUCCEEDED:
+		return ran_a_decode_handover_succeeded(ran_dec, bssmap, tp);
+	case BSS_MAP_MSG_HANDOVER_COMPLETE:
+		return ran_a_decode_handover_complete(ran_dec, bssmap, tp);
+
+	/* From any Handover peer: */
+	case BSS_MAP_MSG_HANDOVER_FAILURE:
+		return ran_a_decode_handover_failure(ran_dec, bssmap, tp);
+
+	default:
+		LOG_RAN_A_DEC(ran_dec, LOGL_ERROR, "Unimplemented msg type: %s\n", gsm0808_bssmap_name(msg_type));
+		return -EINVAL;
+	}
+
+	return -EINVAL;
+}
+
+static int ran_a_decode_l3(struct ran_dec *ran_dec, struct msgb *l3)
+{
+	struct dtap_header *dtap = msgb_l2(l3);
+	struct ran_msg ran_dec_msg = {
+		.msg_type = RAN_MSG_DTAP,
+		.msg_name = "BSSAP DTAP",
+		.dtap = l3,
+	};
+	l3->l3h = l3->l2h + sizeof(struct dtap_header);
+	OMSC_LINKID_CB(l3) = dtap->link_id;
+	return ran_decoded(ran_dec, &ran_dec_msg);
+}
+
+int ran_a_decode_l2(struct ran_dec *ran_dec, struct msgb *bssap)
+{
+	uint8_t bssap_type;
+	OSMO_ASSERT(bssap);
+
+	if (!msgb_l2(bssap) || !msgb_l2len(bssap)) {
+		LOG_RAN_A_DEC(ran_dec, LOGL_ERROR, "Cannot decode L2, msg->l2h is unset / empty: %s\n",
+			      msgb_hexdump(bssap));
+		return -EINVAL;
+	}
+
+	if (msgb_l2len(bssap) < sizeof(struct bssmap_header)) {
+		LOG_RAN_A_DEC(ran_dec, LOGL_ERROR, "The header is too short -- discarding message\n");
+		return -EINVAL;
+	}
+
+	bssap_type = bssap->l2h[0];
+	switch (bssap_type) {
+	case BSSAP_MSG_BSS_MANAGEMENT:
+		return ran_a_decode_bssmap(ran_dec, bssap);
+	case BSSAP_MSG_DTAP:
+		return ran_a_decode_l3(ran_dec, bssap);
+	default:
+		LOG_RAN_A_DEC(ran_dec, LOGL_ERROR, "Unimplemented BSSAP msg type: %s\n", gsm0808_bssap_name(bssap_type));
+		return -EINVAL;
+	}
+}
+
+static struct msgb *ran_a_wrap_dtap(struct msgb *dtap)
+{
+	struct msgb *an_apdu;
+	dtap->l3h = dtap->data;
+	an_apdu = gsm0808_create_dtap(dtap, OMSC_LINKID_CB(dtap));
+	an_apdu->l2h = an_apdu->data;
+	msgb_free(dtap);
+	return an_apdu;
+}
+
+static int ran_a_channel_type_to_speech_codec_list(struct gsm0808_speech_codec_list *scl, const struct gsm0808_channel_type *ct)
+{
+	unsigned int i;
+	int rc;
+
+	memset(scl, 0, sizeof(*scl));
+	for (i = 0; i < ct->perm_spch_len; i++) {
+		rc = gsm0808_speech_codec_from_chan_type(&scl->codec[i], ct->perm_spch[i]);
+		if (rc != 0)
+			return -EINVAL;
+	}
+	scl->len = i;
+
+	return 0;
+}
+
+/* Compose a BSSAP Assignment Command.
+ * Passing an RTP address is optional.
+ * The msub is passed merely for error logging. */
+static struct msgb *ran_a_make_assignment_command(struct osmo_fsm_inst *log_fi,
+						  const struct ran_assignment_command *ac)
+{
+	struct gsm0808_speech_codec_list scl;
+	struct gsm0808_speech_codec_list *use_scl = NULL;
+	struct sockaddr_storage rtp_addr;
+	struct sockaddr_storage *use_rtp_addr = NULL;
+	int rc;
+
+	if (!ac->channel_type) {
+		LOG_RAN_A_ENC(log_fi, LOGL_ERROR, "Assignment Command: missing Channel Type\n");
+		return NULL;
+	}
+
+	if (ac->channel_type->ch_indctr == GSM0808_CHAN_SPEECH) {
+		rc = ran_a_channel_type_to_speech_codec_list(&scl, ac->channel_type);
+		if (rc < 0) {
+			LOG_RAN_A_ENC(log_fi, LOGL_ERROR, "Assignment Command: Cannot translate Channel Type to Speech Codec List\n");
+			return NULL;
+		}
+		use_scl = &scl;
+
+		/* Package RTP-Address data */
+		if (osmo_sockaddr_str_is_set(ac->cn_rtp)) {
+			struct sockaddr_in rtp_addr_in;
+
+			memset(&rtp_addr_in, 0, sizeof(rtp_addr_in));
+			rtp_addr_in.sin_family = AF_INET;
+			rtp_addr_in.sin_port = osmo_htons(ac->cn_rtp->port),
+			rtp_addr_in.sin_addr.s_addr = inet_addr(ac->cn_rtp->ip);
+
+			if (rtp_addr_in.sin_addr.s_addr == INADDR_NONE) {
+				LOG_RAN_A_ENC(log_fi, LOGL_ERROR, "Assignment Command: Invalid RTP-Address\n");
+				return NULL;
+			}
+			if (rtp_addr_in.sin_port == 0) {
+				LOG_RAN_A_ENC(log_fi, LOGL_ERROR, "Assignment Command: Invalid RTP-Port\n");
+				return NULL;
+			}
+
+			memset(&rtp_addr, 0, sizeof(rtp_addr));
+			memcpy(&rtp_addr, &rtp_addr_in, sizeof(rtp_addr_in));
+
+			use_rtp_addr = &rtp_addr;
+		}
+	}
+
+	return gsm0808_create_ass(ac->channel_type, NULL, use_rtp_addr, use_scl, NULL);
+}
+
+/* For an A5/N number a5_n set dst to the matching GSM0808_ALG_ID_A5_<n>. */
+static int a5_n_to_gsm0808_chosen_enc_alg(uint8_t *dst, int a5_n)
+{
+	switch (a5_n) {
+	case 0:
+		*dst = GSM0808_ALG_ID_A5_0;
+		return 0;
+	case 1:
+		*dst = GSM0808_ALG_ID_A5_1;
+		return 0;
+	case 2:
+		*dst = GSM0808_ALG_ID_A5_2;
+		return 0;
+	case 3:
+		*dst = GSM0808_ALG_ID_A5_3;
+		return 0;
+	default:
+		return -ENOTSUP;
+	}
+}
+
+static int make_encrypt_info_perm_algo(struct osmo_fsm_inst *fi, struct gsm0808_encrypt_info *ei,
+				       uint8_t a5_encryption_mask, const struct osmo_gsm48_classmark *cm)
+{
+	int i;
+	int j = 0;
+	for (i = 0; i < 8; i++) {
+		int supported;
+
+		/* A5/n permitted by osmo-msc.cfg? */
+		if (!(a5_encryption_mask & (1 << i)))
+			continue;
+
+		/* A5/n supported by MS? */
+		supported = osmo_gsm48_classmark_supports_a5(cm, i);
+		if (supported != 1)
+			continue;
+
+		if (a5_n_to_gsm0808_chosen_enc_alg(&ei->perm_algo[j], i)) {
+			LOG_RAN_A_ENC(fi, LOGL_ERROR, "Not supported: A5/%d algorithm\n", i);
+			return -1;
+		}
+		j++;
+		ei->perm_algo_len = j;
+	}
+	return 0;
+}
+
+/* For ran_a_make_cipher_mode_command(), for
+ * memcpy(ei.key, cm->vec->kc, sizeof(cm->vec->kc));
+ */
+osmo_static_assert(sizeof(((struct gsm0808_encrypt_info*)0)->key) >= sizeof(((struct osmo_auth_vector*)0)->kc),
+		   gsm0808_encrypt_info_key_fits_osmo_auth_vec_kc);
+static struct msgb *ran_a_make_cipher_mode_command(struct osmo_fsm_inst *fi, const struct ran_cipher_mode_command *cm)
+{
+	struct gsm0808_encrypt_info ei = {};
+	char buf[16 * 2 + 1];
+	const uint8_t cipher_response_mode = 1;
+
+	if (make_encrypt_info_perm_algo(fi, &ei, cm->geran.a5_encryption_mask, cm->classmark))
+		return NULL;
+
+	if (ei.perm_algo_len == 0) {
+		LOG_RAN_A_ENC(fi, LOGL_ERROR, "cannot start ciphering, no intersection between MSC-configured"
+			       " and MS-supported A5 algorithms. MSC: 0x%02x  MS: %s\n",
+			       cm->geran.a5_encryption_mask, osmo_gsm48_classmark_a5_name(cm->classmark));
+		return NULL;
+	}
+
+	/* In case of UMTS AKA, the Kc for ciphering must be derived from the 3G auth
+	 * tokens.  vec->kc was calculated from the GSM algorithm and is not
+	 * necessarily a match for the UMTS AKA tokens. */
+	if (cm->geran.umts_aka)
+		osmo_auth_c3(ei.key, cm->vec->ck, cm->vec->ik);
+	else
+		memcpy(ei.key, cm->vec->kc, sizeof(cm->vec->kc));
+	ei.key_len = sizeof(cm->vec->kc);
+
+	/* Store chosen GERAN key where the caller asked it to be stored.
+	 * alg_id remains unknown until we receive a Cipher Mode Complete from the BSC */
+	if (cm->geran.chosen_key) {
+		if (ei.key_len > sizeof(cm->geran.chosen_key->key)) {
+			LOG_RAN_A_ENC(fi, LOGL_ERROR, "Chosen key is larger than I can store\n");
+			return NULL;
+		}
+		memcpy(cm->geran.chosen_key->key, ei.key, ei.key_len);
+		cm->geran.chosen_key->key_len = ei.key_len;
+	}
+
+	LOG_RAN_A_ENC(fi, LOGL_DEBUG, "Tx BSSMAP CIPHER MODE COMMAND to BSC, %u ciphers (%s) key %s\n",
+		       ei.perm_algo_len, osmo_hexdump_nospc(ei.perm_algo, ei.perm_algo_len),
+		       osmo_hexdump_buf(buf, sizeof(buf), ei.key, ei.key_len, NULL, false));
+	return gsm0808_create_cipher(&ei, cm->geran.retrieve_imeisv ? &cipher_response_mode : NULL);
+}
+
+struct msgb *ran_a_make_handover_request(struct osmo_fsm_inst *log_fi, const struct ran_handover_request *n)
+{
+	struct sockaddr_storage ss;
+	struct gsm0808_handover_request r = {
+		.cell_identifier_serving = n->cell_id_serving,
+		.cell_identifier_target = n->cell_id_target,
+		.cause = n->bssap_cause,
+		.current_channel_type_1_present = n->current_channel_type_1_present,
+		.current_channel_type_1 = n->current_channel_type_1,
+
+		.speech_version_used = n->speech_version_used,
+
+		.chosen_encryption_algorithm_serving = n->geran.chosen_encryption->alg_id,
+
+		.old_bss_to_new_bss_info_raw = n->old_bss_to_new_bss_info_raw,
+		.old_bss_to_new_bss_info_raw_len = n->old_bss_to_new_bss_info_raw_len,
+
+		.imsi = n->imsi,
+		.codec_list_msc_preferred = n->codec_list_msc_preferred,
+		.call_id = n->call_id,
+		.global_call_reference = n->global_call_reference,
+		.global_call_reference_len = n->global_call_reference_len,
+	};
+
+	if (!n->geran.channel_type) {
+		LOG_RAN_A_ENC(log_fi, LOGL_ERROR, "Channel Type required for encoding Handover Request in BSSAP\n");
+		return NULL;
+	}
+	r.channel_type = *n->geran.channel_type;
+
+	/* Encryption Information */
+	make_encrypt_info_perm_algo(log_fi, &r.encryption_information, n->geran.a5_encryption_mask, n->classmark);
+	if (n->geran.chosen_encryption && n->geran.chosen_encryption->key_len) {
+		if (n->geran.chosen_encryption->key_len > sizeof(r.encryption_information.key)) {
+			LOG_RAN_A_ENC(log_fi, LOGL_ERROR, "Handover Request: invalid chosen encryption key size %u\n",
+				       n->geran.chosen_encryption->key_len);
+			return NULL;
+		}
+		memcpy(r.encryption_information.key,
+		       n->geran.chosen_encryption->key, n->geran.chosen_encryption->key_len);
+		r.encryption_information.key_len = n->geran.chosen_encryption->key_len;
+	}
+
+	if (n->classmark)
+		r.classmark_information = *n->classmark;
+
+	if (osmo_sockaddr_str_is_set(n->rtp_ran_local)) {
+		if (osmo_sockaddr_str_to_sockaddr(n->rtp_ran_local, &ss)) {
+			LOG_RAN_A_ENC(log_fi, LOGL_ERROR,
+				       "Handover Request: invalid AoIP Transport Layer address/port: "
+				       OSMO_SOCKADDR_STR_FMT "\n", OSMO_SOCKADDR_STR_FMT_ARGS(n->rtp_ran_local));
+			return NULL;
+		}
+		r.aoip_transport_layer = &ss;
+	}
+
+	return gsm0808_create_handover_request(&r);
+}
+
+static struct msgb *ran_a_make_handover_request_ack(struct osmo_fsm_inst *caller_fi, const struct ran_handover_request_ack *r)
+{
+	struct sockaddr_storage ss;
+	struct gsm0808_handover_request_ack params = {
+		.l3_info = r->rr_ho_command,
+		.l3_info_len = r->rr_ho_command_len,
+		.chosen_channel_present = r->chosen_channel_present,
+		.chosen_channel = r->chosen_channel,
+		.chosen_encr_alg = r->chosen_encr_alg,
+		.chosen_speech_version = r->chosen_speech_version,
+	};
+
+	if (osmo_sockaddr_str_is_set(&r->remote_rtp)) {
+		osmo_sockaddr_str_to_sockaddr(&r->remote_rtp, &ss);
+		params.aoip_transport_layer = &ss;
+	}
+
+	return gsm0808_create_handover_request_ack2(&params);
+}
+
+struct msgb *ran_a_make_handover_command(struct osmo_fsm_inst *log_fi, const struct ran_handover_command *n)
+{
+	struct gsm0808_handover_command c = {
+		.l3_info = n->rr_ho_command,
+		.l3_info_len = n->rr_ho_command_len,
+	};
+
+	return gsm0808_create_handover_command(&c);
+}
+
+struct msgb *ran_a_make_handover_failure(struct osmo_fsm_inst *log_fi, const struct ran_msg *msg)
+{
+	struct gsm0808_handover_failure params = {
+		.cause = msg->handover_failure.cause,
+	};
+	return gsm0808_create_handover_failure(&params);
+}
+
+static struct msgb *_ran_a_encode(struct osmo_fsm_inst *caller_fi, const struct ran_msg *ran_enc_msg)
+{
+
+	LOG_RAN_A_ENC(caller_fi, LOGL_DEBUG, "%s\n", ran_msg_type_name(ran_enc_msg->msg_type));
+
+	switch (ran_enc_msg->msg_type) {
+
+	case RAN_MSG_DTAP:
+		return ran_a_wrap_dtap(ran_enc_msg->dtap);
+
+	case RAN_MSG_CLASSMARK_REQUEST:
+		return gsm0808_create_classmark_request();
+
+	case RAN_MSG_CLEAR_COMMAND:
+		return gsm0808_create_clear_command2(ran_enc_msg->clear_command.gsm0808_cause,
+						     ran_enc_msg->clear_command.csfb_ind);
+
+	case RAN_MSG_ASSIGNMENT_COMMAND:
+		return ran_a_make_assignment_command(caller_fi, &ran_enc_msg->assignment_command);
+
+	case RAN_MSG_CIPHER_MODE_COMMAND:
+		return ran_a_make_cipher_mode_command(caller_fi, &ran_enc_msg->cipher_mode_command);
+
+	case RAN_MSG_HANDOVER_REQUIRED_REJECT:
+		return gsm0808_create_handover_required_reject(&ran_enc_msg->handover_required_reject);
+
+	case RAN_MSG_HANDOVER_REQUEST:
+		return ran_a_make_handover_request(caller_fi, &ran_enc_msg->handover_request);
+
+	case RAN_MSG_HANDOVER_REQUEST_ACK:
+		return ran_a_make_handover_request_ack(caller_fi, &ran_enc_msg->handover_request_ack);
+
+	case RAN_MSG_HANDOVER_COMMAND:
+		return ran_a_make_handover_command(caller_fi, &ran_enc_msg->handover_command);
+
+	case RAN_MSG_HANDOVER_SUCCEEDED:
+		return gsm0808_create_handover_succeeded();
+
+	case RAN_MSG_HANDOVER_FAILURE:
+		return ran_a_make_handover_failure(caller_fi, ran_enc_msg);
+
+	default:
+		LOG_RAN_A_ENC(caller_fi, LOGL_ERROR, "Unimplemented RAN-encode message type: %s\n",
+			       ran_msg_type_name(ran_enc_msg->msg_type));
+		return NULL;
+	}
+}
+
+struct msgb *ran_a_encode(struct osmo_fsm_inst *caller_fi, const struct ran_msg *ran_enc_msg)
+{
+	struct msgb *msg = _ran_a_encode(caller_fi, ran_enc_msg);
+
+	if (!msg)
+		return NULL;
+
+	msg->l2h = msg->data;
+
+	/* some consistency checks to ensure we don't send invalid length */
+	switch (msg->l2h[0]) {
+	case BSSAP_MSG_DTAP:
+		OSMO_ASSERT(msgb_l2len(msg) == msg->l2h[2] + 3);
+		break;
+	case BSSAP_MSG_BSS_MANAGEMENT:
+		OSMO_ASSERT(msgb_l2len(msg) == msg->l2h[1] + 2);
+		break;
+	default:
+		break;
+	}
+
+	return msg;
+}
+
+/* Return 1 for a RESET, 2 for a RESET ACK message, 0 otherwise */
+enum reset_msg_type bssmap_is_reset_msg(const struct sccp_ran_inst *sri, const struct msgb *l2)
+{
+	struct bssmap_header *bs = (struct bssmap_header *)msgb_l2(l2);
+
+	if (!bs
+	    || msgb_l2len(l2) < (sizeof(*bs) + 1)
+	    || bs->type != BSSAP_MSG_BSS_MANAGEMENT)
+		return SCCP_RAN_MSG_NON_RESET;
+
+	switch (l2->l2h[sizeof(*bs)]) {
+	case BSS_MAP_MSG_RESET:
+		return SCCP_RAN_MSG_RESET;
+	case BSS_MAP_MSG_RESET_ACKNOWLEDGE:
+		return SCCP_RAN_MSG_RESET_ACK;
+	default:
+		return SCCP_RAN_MSG_NON_RESET;
+	}
+}
+
+struct msgb *bssmap_make_reset_msg(const struct sccp_ran_inst *sri, enum reset_msg_type type)
+{
+	switch (type) {
+	case SCCP_RAN_MSG_RESET:
+		return gsm0808_create_reset();
+	case SCCP_RAN_MSG_RESET_ACK:
+		return gsm0808_create_reset_ack();
+	default:
+		return NULL;
+	}
+}
+
+struct msgb *bssmap_make_paging_msg(const struct sccp_ran_inst *sri, const struct gsm0808_cell_id *page_cell_id,
+				    const char *imsi, uint32_t tmsi, enum paging_cause cause)
+{
+	struct gsm0808_cell_id_list2 cil;
+	gsm0808_cell_id_to_list(&cil, page_cell_id);
+	return gsm0808_create_paging2(imsi, tmsi == GSM_RESERVED_TMSI ? NULL : &tmsi, &cil, NULL);
+}
+
+const char *bssmap_msg_name(const struct sccp_ran_inst *sri, const struct msgb *l2)
+{
+	struct bssmap_header *bs;
+
+	if (!l2->l2h)
+		return "?";
+
+	bs = (struct bssmap_header *)msgb_l2(l2);
+	switch (bs->type) {
+	case BSSAP_MSG_BSS_MANAGEMENT:
+		return gsm0808_bssmap_name(l2->l2h[0]);
+	case BSSAP_MSG_DTAP:
+		return "DTAP";
+	default:
+		return "?";
+	}
+}