diff --git a/openbsc/src/libmgcp/mgcp_network.c b/openbsc/src/libmgcp/mgcp_network.c
index 393a9e5..05c3e77 100644
--- a/openbsc/src/libmgcp/mgcp_network.c
+++ b/openbsc/src/libmgcp/mgcp_network.c
@@ -353,6 +353,19 @@
 	return 0;
 }
 
+void mgcp_get_net_downlink_format_default(struct mgcp_endpoint *endp,
+					  int *payload_type,
+					  const char**audio_name,
+					  const char**fmtp_extra)
+{
+	/* Use the BTS side parameters when passing the SDP data (for
+	 * downlink) to the net peer.
+	 */
+	*payload_type = endp->bts_end.payload_type;
+	*audio_name = endp->bts_end.audio_name;
+	*fmtp_extra = endp->bts_end.fmtp_extra;
+}
+
 /**
  * The RFC 3550 Appendix A assumes there are multiple sources but
  * some of the supported endpoints (e.g. the nanoBTS) can only handle
diff --git a/openbsc/src/libmgcp/mgcp_protocol.c b/openbsc/src/libmgcp/mgcp_protocol.c
index 862bf17..7837378 100644
--- a/openbsc/src/libmgcp/mgcp_protocol.c
+++ b/openbsc/src/libmgcp/mgcp_protocol.c
@@ -245,12 +245,15 @@
 					     const char *msg, const char *trans_id)
 {
 	const char *addr = endp->cfg->local_ip;
-	const char *fmtp_extra = endp->bts_end.fmtp_extra;
-	const char *audio_name = endp->bts_end.audio_name;
-	int payload_type = endp->bts_end.payload_type;
+	const char *fmtp_extra;
+	const char *audio_name;
+	int payload_type;
 	char sdp_record[4096];
 	int len;
 
+	endp->cfg->get_net_downlink_format_cb(endp, &payload_type,
+					      &audio_name, &fmtp_extra);
+
 	if (!addr)
 		addr = endp->cfg->source_addr;
 
@@ -1268,6 +1271,8 @@
 	cfg->rtp_processing_cb = &mgcp_rtp_processing_default;
 	cfg->setup_rtp_processing_cb = &mgcp_setup_rtp_processing_default;
 
+	cfg->get_net_downlink_format_cb = &mgcp_get_net_downlink_format_default;
+
 	/* default trunk handling */
 	cfg->trunk.cfg = cfg;
 	cfg->trunk.trunk_nr = 0;
@@ -1424,8 +1429,12 @@
 {
 	char buf[2096];
 	int len;
-	const char *audio_name = endp->bts_end.audio_name;
-	int payload_type = endp->bts_end.payload_type;
+	const char *fmtp_extra;
+	const char *audio_name;
+	int payload_type;
+
+	endp->cfg->get_net_downlink_format_cb(endp, &payload_type,
+					      &audio_name, &fmtp_extra);
 
 	/* hardcoded to AMR right now, we do not know the real type at this point */
 	len = snprintf(buf, sizeof(buf),