diff --git a/include/osmocom/msc/call_leg.h b/include/osmocom/msc/call_leg.h
index d8380f5..f35816c 100644
--- a/include/osmocom/msc/call_leg.h
+++ b/include/osmocom/msc/call_leg.h
@@ -44,6 +44,8 @@
 
 	/* Prevent events from deallocating for certain release code paths, to prevent use-after-free problems. */
 	bool deallocating;
+
+	bool ran_peer_supports_osmux;
 };
 
 enum call_leg_event {
diff --git a/include/osmocom/msc/ran_msg.h b/include/osmocom/msc/ran_msg.h
index 4d0485d..af0822b 100644
--- a/include/osmocom/msc/ran_msg.h
+++ b/include/osmocom/msc/ran_msg.h
@@ -84,6 +84,8 @@
 	const struct osmo_sockaddr_str *cn_rtp;
 	const struct gsm0808_channel_type *channel_type;
 	enum nsap_addr_enc rab_assign_addr_enc;
+	bool osmux_present;
+	uint8_t osmux_cid;
 };
 
 struct ran_cipher_mode_command {
@@ -223,6 +225,8 @@
 			struct osmo_sockaddr_str remote_rtp;
 			bool codec_present;
 			enum mgcp_codecs codec;
+			bool osmux_present;
+			uint8_t osmux_cid;
 		} assignment_complete;
 		struct {
 			enum gsm0808_cause bssap_cause;
diff --git a/include/osmocom/msc/rtp_stream.h b/include/osmocom/msc/rtp_stream.h
index 794e806..c53c4f1 100644
--- a/include/osmocom/msc/rtp_stream.h
+++ b/include/osmocom/msc/rtp_stream.h
@@ -44,6 +44,15 @@
 	struct osmo_mgcpc_ep_ci *ci;
 
 	enum mgcp_connection_mode crcx_conn_mode;
+
+	/* configured to use Osmux */
+	bool use_osmux;
+	/* Allocated by our MGW, negative means invalid, not yet known */
+	int local_osmux_cid;
+	/* Allocated by BSC MGW, negative means invalid, not yet known */
+	int remote_osmux_cid;
+	 /* Whether remote_osmux_cid has been communicated to MGW */
+	bool remote_osmux_cid_sent_to_mgw;
 };
 
 #define RTP_STREAM_FMT "local=" RTP_IP_PORT_FMT ",remote=" RTP_IP_PORT_FMT
@@ -57,6 +66,7 @@
 
 void rtp_stream_set_codec(struct rtp_stream *rtps, enum mgcp_codecs codec);
 void rtp_stream_set_remote_addr(struct rtp_stream *rtps, const struct osmo_sockaddr_str *r);
+void rtp_stream_set_remote_osmux_cid(struct rtp_stream *rtps, uint8_t osmux_cid);
 int rtp_stream_commit(struct rtp_stream *rtps);
 
 void rtp_stream_release(struct rtp_stream *rtps);