diff --git a/library/MGCP_Templates.ttcn b/library/MGCP_Templates.ttcn
index 4736aaa..dae379e 100644
--- a/library/MGCP_Templates.ttcn
+++ b/library/MGCP_Templates.ttcn
@@ -198,6 +198,7 @@
 	}
 
 	template MgcpResponse ts_MDCX_ACK(MgcpTransId trans_id, MgcpConnectionId conn_id, template SDP_Message sdp := omit) := ts_CRCX_ACK(trans_id, conn_id, sdp);
+	template MgcpResponse ts_MDCX_ACK_osmux(MgcpTransId trans_id, MgcpConnectionId conn_id, MgcpOsmuxCID osmux_cid, template SDP_Message sdp := omit) := ts_CRCX_ACK_osmux(trans_id, conn_id, osmux_cid, sdp);
 
 	/* have a function that generates a template, rather than a template in order to handle
 	 * optional parameters */
diff --git a/msc/BSC_ConnectionHandler.ttcn b/msc/BSC_ConnectionHandler.ttcn
index 29cde36..f83407a 100644
--- a/msc/BSC_ConnectionHandler.ttcn
+++ b/msc/BSC_ConnectionHandler.ttcn
@@ -83,7 +83,8 @@
 	boolean gsup_enable,
 	integer ran_idx,
 	boolean use_umts_aka,
-	boolean ran_is_geran
+	boolean ran_is_geran,
+	boolean use_osmux
 };
 
 /* get a one-octet bitmaks of supported algorithms based on Classmark information */
@@ -172,9 +173,9 @@
 
 	log("BSSMAP_BscUnitdataCallback");
 	/* answer all RESET with RESET ACK */
-	if (match(bssap, tr_BSSMAP_Reset)){
+	if (match(bssap, tr_BSSMAP_Reset(g_ran_ops.use_osmux))){
 		log("BSSMAP_BscUnitdataCallback: Responding to RESET with RESET-ACK");
-		resp := ts_BSSMAP_ResetAck;
+		resp := ts_BSSMAP_ResetAck(g_ran_ops.use_osmux);
 	}
 
 	/* FIXME: Handle paging, etc. */
@@ -187,7 +188,7 @@
 
 	log("RANAP_RncUnitdataCallback");
 	/* answer all RESET with RESET ACK */
-	if (match(ranap, tr_RANAP_Reset)) {
+	if (match(ranap, tr_RANAP_Reset())) {
 		log("RANAP_RncUnitdataCallback: Responding to RESET with RESET-ACK");
 		var CN_DomainIndicator dom;
 		dom := ranap.initiatingMessage.value_.Reset.protocolIEs[1].value_.cN_DomainIndicator;
@@ -593,7 +594,9 @@
 	MgcpCallId mgcp_call_id optional,		/* MGCP Call ID; CallAgent allocated */
 	MgcpEndpoint mgcp_ep optional			/* MGCP Endpoint, CallAgent or MGW allocated */,
 	MgcpConnectionId mgcp_connection_id_bss,	/* MGCP Connection ID BSS Side */
-	MgcpConnectionId mgcp_connection_id_mss		/* MGCP Connection ID MSS Side */
+	MgcpConnectionId mgcp_connection_id_mss,	/* MGCP Connection ID MSS Side */
+
+	boolean use_osmux				/* MSC is expected to use Osmux for this call */
 }
 
 template (value) CallParameters t_CallParams(hexstring called, integer tid) := {
@@ -618,7 +621,8 @@
 	mgcp_call_id := omit,
 	mgcp_ep := omit,
 	mgcp_connection_id_bss := '0'H,//
-	mgcp_connection_id_mss := '0'H //
+	mgcp_connection_id_mss := '0'H,//
+	use_osmux := false
 };
 
 /* Allocate a call reference and send SETUP via MNCC to MSC */
@@ -643,6 +647,9 @@
 runs on BSC_ConnHdlr {
 	var MNCC_PDU mncc;
 	var MgcpCommand mgcp_cmd;
+	var template MgcpResponse mgcp_resp;
+	var MgcpOsmuxCID osmux_cid;
+	var PDU_BSSAP bssap;
 
 	f_ran_register_imsi(g_pars.imsi, g_pars.tmsi);
 
@@ -682,8 +689,19 @@
 							{ valueof(ts_SDP_rtpmap(cpars.rtp_payload_type,
 										cpars.rtp_sdp_format)),
 							  valueof(ts_SDP_ptime(20)) }));
-		var template MgcpResponse mgcp_resp;
-		mgcp_resp := ts_CRCX_ACK(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_bss, sdp);
+
+		if (cpars.use_osmux) {
+			osmux_cid := f_MgcpCmd_extract_osmux_cid(mgcp_cmd);
+			if (osmux_cid != -1) { /* we expect MSC to use wildcard here */
+				setverdict(fail, "MSC using unexpected CID " & int2str(osmux_cid) & " != -1");
+				mtc.stop;
+			}
+			osmux_cid := 0;
+			mgcp_resp := ts_CRCX_ACK_osmux(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_bss, osmux_cid, sdp);
+		} else {
+			mgcp_resp := ts_CRCX_ACK(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_bss, sdp);
+		}
+
 		f_mgcp_par_append(mgcp_resp.params, ts_MgcpParSpecEP(cpars.mgcp_ep));
 		MGCP.send(mgcp_resp);
 		}
@@ -707,15 +725,30 @@
 			}
 
 		/* expect the MSC to trigger a BSSMAP ASSIGNMENT */
-		[] BSSAP.receive(tr_BSSMAP_AssignmentReq(omit, tla_ass)) {
+		[] BSSAP.receive(tr_BSSMAP_AssignmentReq(omit, tla_ass)) -> value bssap {
 			var BSSMAP_IE_AoIP_TransportLayerAddress tla;
 			var BSSMAP_IE_SpeechCodec codec;
+			var BSSMAP_IE_Osmo_OsmuxCID osmuxCID;
 			log("f_mt_call_complete 6");
 
 			tla := valueof(ts_BSSMAP_IE_AoIP_TLA4(f_inet_addr(cpars.bss_rtp_ip), cpars.bss_rtp_port));
 			codec := valueof(ts_BSSMAP_IE_SpeechCodec({ts_CodecFR}));
 
-			BSSAP.send(ts_BSSMAP_AssignmentComplete(omit, tla, codec));
+			if (cpars.use_osmux) {
+				if (not ispresent(bssap.pdu.bssmap.assignmentRequest.osmuxCID)) {
+					setverdict(fail, "MSC sent AssignReq without expected OsmuxCID IE");
+					mtc.stop;
+				}
+				osmuxCID := valueof(ts_OsmuxCID(0));
+				if (cpars.use_osmux and not match(bssap.pdu.bssmap.assignmentRequest.osmuxCID, osmuxCID)) {
+					setverdict(fail, "MSC sent AssignReq without expected OsmuxCID IE");
+					mtc.stop;
+				}
+				bssap := valueof(ts_BSSMAP_AssignmentComplete(omit, tla, codec, osmuxCID));
+			} else {
+				bssap := valueof(ts_BSSMAP_AssignmentComplete(omit, tla, codec));
+			}
+			BSSAP.send(bssap);
 
 			BSSAP.send(ts_PDU_DTAP_MO(ts_ML3_MO_CC_CONNECT(cpars.transaction_id)));
 			}
@@ -737,8 +770,18 @@
 								{ int2str(cpars.rtp_payload_type) },
 								{ valueof(ts_SDP_rtpmap(cpars.rtp_payload_type,
 											cpars.rtp_sdp_format)),
-								  valueof(ts_SDP_ptime(20)) }));
-			MGCP.send(ts_MDCX_ACK(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_mss, sdp));
+											valueof(ts_SDP_ptime(20)) }));
+			if (cpars.use_osmux) {
+				osmux_cid := f_MgcpCmd_extract_osmux_cid(mgcp_cmd);
+				if (osmux_cid != 0) { /* we expect MSC to use specific CID here */
+					setverdict(fail, "MSC using unexpected CID " & int2str(osmux_cid) & " != 0");
+					mtc.stop;
+				}
+				mgcp_resp := ts_MDCX_ACK_osmux(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_bss, osmux_cid, sdp);
+			} else {
+				mgcp_resp := ts_MDCX_ACK(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_mss, sdp);
+			}
+			MGCP.send(mgcp_resp);
 			}
 
 		/* MDCX setting up the CN side remote RTP address received from MNCC CONNECT */
@@ -807,7 +850,10 @@
 
 	var MNCC_PDU mncc;
 	var MgcpCommand mgcp_cmd;
+	var template MgcpResponse mgcp_resp;
 	var boolean respond_to_dlcx;
+	var PDU_BSSAP bssap;
+	var MgcpOsmuxCID osmux_cid;
 
 	if (cpars.emergency) {
 		f_establish_fully(EST_TYPE_EMERG_CALL);
@@ -847,6 +893,10 @@
 			cpars.mgcp_ep := mgcp_cmd.line.ep;
 		}
 
+		if (cpars.use_osmux) {
+			osmux_cid := f_MgcpCmd_extract_osmux_cid(mgcp_cmd);
+		}
+
 		var SDP_Message sdp := valueof(ts_SDP(cpars.mgw_rtp_ip_bss, cpars.mgw_rtp_ip_bss,
 							hex2str(cpars.mgcp_call_id), "42",
 							cpars.mgw_rtp_port_bss,
@@ -855,8 +905,17 @@
 										cpars.rtp_sdp_format)),
 							  valueof(ts_SDP_ptime(20)) }));
 
-		var template MgcpResponse mgcp_resp;
-		mgcp_resp := ts_CRCX_ACK(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_bss, sdp);
+		if (cpars.use_osmux) {
+			osmux_cid := f_MgcpCmd_extract_osmux_cid(mgcp_cmd);
+			if (osmux_cid != -1) { /* we expect MSC to use wildcard here */
+				setverdict(fail, "MSC using unexpected CID " & int2str(osmux_cid) & " != -1");
+				mtc.stop;
+			}
+			osmux_cid := 0;
+			mgcp_resp := ts_CRCX_ACK_osmux(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_bss, osmux_cid, sdp);
+		} else {
+			mgcp_resp := ts_CRCX_ACK(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_bss, sdp);
+		}
 		f_mgcp_par_append(mgcp_resp.params, ts_MgcpParSpecEP(cpars.mgcp_ep));
 		MGCP.send(mgcp_resp);
 		}
@@ -871,14 +930,30 @@
 		MNCC.send(ts_MNCC_ALERT_req(cpars.mncc_callref));
 		}
 
-	//[g_pars.ran_is_geran] BSSAP.receive(tr_BSSMAP_AssignmentReq(omit, tla_ass)) {
-	[] BSSAP.receive(tr_BSSMAP_AssignmentReq(omit, tla_ass)) {
+	//[g_pars.ran_is_geran] BSSAP.receive(tr_BSSMAP_AssignmentReq(omit, tla_ass)) -> value bssap {
+	[] BSSAP.receive(tr_BSSMAP_AssignmentReq(omit, tla_ass)) -> value bssap {
 		log("f_mo_call_establish 4: rx Assignment Request");
 		var BSSMAP_IE_AoIP_TransportLayerAddress tla;
 		var BSSMAP_IE_SpeechCodec codec;
+		var BSSMAP_IE_Osmo_OsmuxCID osmuxCID;
+
 		tla := valueof(ts_BSSMAP_IE_AoIP_TLA4(f_inet_addr(cpars.bss_rtp_ip), cpars.bss_rtp_port));
 		codec := valueof(ts_BSSMAP_IE_SpeechCodec({ts_CodecFR}));
-		BSSAP.send(ts_BSSMAP_AssignmentComplete(omit, tla, codec));
+		if (cpars.use_osmux) {
+			if (not ispresent(bssap.pdu.bssmap.assignmentRequest.osmuxCID)) {
+				setverdict(fail, "MSC sent AssignReq without expected OsmuxCID IE");
+				mtc.stop;
+			}
+			osmuxCID := valueof(ts_OsmuxCID(0));
+			if (cpars.use_osmux and not match(bssap.pdu.bssmap.assignmentRequest.osmuxCID, osmuxCID)) {
+				setverdict(fail, "MSC sent AssignReq without expected OsmuxCID IE");
+				mtc.stop;
+			}
+			bssap := valueof(ts_BSSMAP_AssignmentComplete(omit, tla, codec, osmuxCID));
+		} else {
+			bssap := valueof(ts_BSSMAP_AssignmentComplete(omit, tla, codec));
+		}
+		BSSAP.send(bssap);
 		}
 	/*
 	[!g_pars.ran_is_geran] BSSAP.receive(tr_RANAP_RabAssReq(rab_sml)) {
@@ -896,7 +971,18 @@
 							{ valueof(ts_SDP_rtpmap(cpars.rtp_payload_type,
 										cpars.rtp_sdp_format)),
 							  valueof(ts_SDP_ptime(20)) }));
-		MGCP.send(ts_MDCX_ACK(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_mss, sdp));
+
+		if (cpars.use_osmux) {
+			osmux_cid := f_MgcpCmd_extract_osmux_cid(mgcp_cmd);
+			if (osmux_cid != 0) { /* we expect MSC to use specific CID here */
+				setverdict(fail, "MSC using unexpected CID " & int2str(osmux_cid) & " != 0");
+				mtc.stop;
+			}
+			mgcp_resp := ts_MDCX_ACK_osmux(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_bss, osmux_cid, sdp);
+		} else {
+			mgcp_resp := ts_MDCX_ACK(mgcp_cmd.line.trans_id, cpars.mgcp_connection_id_mss, sdp);
+		}
+		MGCP.send(mgcp_resp);
 		}
 
 	/* Second MGCP CRCX (this time for MSS/CN side) */
diff --git a/msc/MSC_Tests.ttcn b/msc/MSC_Tests.ttcn
index b64b872..0d6083e 100644
--- a/msc/MSC_Tests.ttcn
+++ b/msc/MSC_Tests.ttcn
@@ -275,7 +275,7 @@
 	}
 }
 
-function f_init(integer num_bsc := 1, boolean sgsap := false, boolean gsup := true) runs on MTC_CT {
+function f_init(integer num_bsc := 1, boolean sgsap := false, boolean gsup := true, boolean osmux := false) runs on MTC_CT {
 
 	if (g_initialized == true) {
 		return;
@@ -288,7 +288,9 @@
 
 	for (var integer i := 0; i < num_bsc; i := i + 1) {
 		if (isbound(mp_bssap_cfg[i])) {
-			f_ran_adapter_init(g_bssap[i], mp_bssap_cfg[i], "MSC_Test_" & int2str(i), BSC_RanOps);
+			var RanOps ranops := BSC_RanOps;
+			ranops.use_osmux := osmux;
+			f_ran_adapter_init(g_bssap[i], mp_bssap_cfg[i], "MSC_Test_" & int2str(i), ranops);
 			f_ran_adapter_start(g_bssap[i]);
 		} else {
 			testcase.stop("missing BSSAP configuration");
@@ -334,7 +336,7 @@
 
 /* FIXME: move into BSC_ConnectionHandler? */
 function f_init_pars(integer imsi_suffix, boolean sgsap := false, boolean gsup := true, integer ran_idx := 0,
-		     boolean ran_is_geran := true)
+		     boolean ran_is_geran := true, boolean use_osmux := false)
 runs on MTC_CT return BSC_ConnHdlrPars {
 	var BSC_ConnHdlrNetworkPars net_pars := {
 		kc_support := '0A'O,	/* A5/1 and A5/3 enabled */
@@ -364,7 +366,8 @@
 		gsup_enable := gsup,
 		ran_idx := ran_idx,
 		use_umts_aka := false,
-		ran_is_geran := ran_is_geran
+		ran_is_geran := ran_is_geran,
+		use_osmux := use_osmux
 	};
 	if (not ran_is_geran) {
 		pars.use_umts_aka := true;
@@ -407,9 +410,9 @@
 	return vc_conn;
 }
 
-function f_start_handler(void_fn fn, integer imsi_suffix, integer ran_idx := 0, boolean ran_is_geran := true)
+function f_start_handler(void_fn fn, integer imsi_suffix, integer ran_idx := 0, boolean ran_is_geran := true, boolean use_osmux := false)
 runs on MTC_CT return BSC_ConnHdlr {
-	return f_start_handler_with_pars(fn, f_init_pars(imsi_suffix, ran_idx := ran_idx, ran_is_geran := ran_is_geran));
+	return f_start_handler_with_pars(fn, f_init_pars(imsi_suffix, ran_idx := ran_idx, ran_is_geran := ran_is_geran, use_osmux := use_osmux));
 }
 
 private function f_tc_lu_imsi_noauth_tmsi(charstring id, BSC_ConnHdlrPars pars) runs on BSC_ConnHdlr {
@@ -1711,6 +1714,7 @@
 	cpars.bss_rtp_port := 1110;
 	cpars.mgcp_connection_id_bss := '10004'H;
 	cpars.mgcp_connection_id_mss := '10005'H;
+	cpars.use_osmux := pars.use_osmux;
 
 	/* Note: This is an optional parameter. When the call-agent (MSC) does
 	 * supply a full endpoint name this setting will be overwritten. */
@@ -1727,6 +1731,15 @@
 	vc_conn.done;
 }
 
+testcase TC_lu_and_mt_call_osmux() runs on MTC_CT {
+	var BSC_ConnHdlr vc_conn;
+	f_init(1, false, true, true);
+	f_vty_config(MSCVTY, "msc", "osmux on");
+
+	vc_conn := f_start_handler(refers(f_tc_lu_and_mt_call), 39, 0, true, true);
+	vc_conn.done;
+}
+
 /* Test MO Call SETUP with DTMF */
 private function f_tc_mo_setup_dtmf_dup(charstring id, BSC_ConnHdlrPars pars) runs on BSC_ConnHdlr {
 	f_init_handler(pars);
@@ -5303,6 +5316,8 @@
 	execute( TC_lu_imsi_auth_tmsi_encr_3_1_log_msc_debug() );
 	execute( TC_gsup_mt_multi_part_sms() );
 	execute( TC_mo_cc_bssmap_clear() );
+
+	execute( TC_lu_and_mt_call_osmux() );
 }