diff --git a/gsm.cpp b/gsm.cpp
index 9ab9650..c99a867 100644
--- a/gsm.cpp
+++ b/gsm.cpp
@@ -138,10 +138,17 @@ int send_and_free_mncc(struct lcr_gsm *lcr_gsm, unsigned int msg_type, void *dat
 void Pgsm::send_mncc_rtp_connect(void)
 {
 	struct gsm_mncc_rtp *nrtp;
+	struct sockaddr_in *addr;
 
 	nrtp = (struct gsm_mncc_rtp *) create_mncc(MNCC_RTP_CONNECT, p_g_callref);
-	nrtp->ip = p_g_rtp_ip_remote;
-	nrtp->port = p_g_rtp_port_remote;
+
+	addr = reinterpret_cast<struct sockaddr_in *>(&nrtp->addr);
+	*addr = (struct sockaddr_in) {
+		.sin_family = AF_INET,
+		.sin_port = htons(p_g_rtp_port_remote),
+		.sin_addr = { .s_addr = htonl(p_g_rtp_ip_remote) },
+	};
+
 	switch (p_g_media_type) {
 	case MEDIA_TYPE_GSM:
 		nrtp->payload_msg_type = GSM_TCHF_FRAME;
@@ -888,17 +895,24 @@ void Pgsm::rtp_create_ind(unsigned int msg_type, unsigned int callref, struct gs
 
 	/* send queued setup, as we received remote RTP info */
 	if (p_g_setup_pending) {
+		const struct sockaddr_in *addr;
 		struct lcr_msg *message;
 
+		addr = reinterpret_cast<const struct sockaddr_in *>(&rtp->addr);
+		assert(addr->sin_family == AF_INET); // XXX
+
 		message = p_g_setup_pending;
-		PDEBUG(DEBUG_GSM, "Got RTP peer info (%08x,%d) forwarding setup\n", rtp->ip, rtp->port);
-		message->param.setup.rtpinfo.ip = rtp->ip;
-		message->param.setup.rtpinfo.port = rtp->port;
+		message->param.setup.rtpinfo.ip = ntohl(addr->sin_addr.s_addr);
+		message->param.setup.rtpinfo.port = ntohs(addr->sin_port);
+		PDEBUG(DEBUG_GSM, "Got RTP peer info (%08x,%d) forwarding setup\n",
+		       message->param.setup.rtpinfo.ip,
+		       message->param.setup.rtpinfo.port);
 		message_put(message);
 		p_g_setup_pending = NULL;
 	}
 	if (p_g_connect_pending) {
-		PDEBUG(DEBUG_GSM, "Got RTP peer info (%08x,%d) connecting RTP... \n", rtp->ip, rtp->port);
+		PDEBUG(DEBUG_GSM, "Got RTP peer info (%08x,%d) connecting RTP... \n",
+		       p_g_rtp_ip_remote, p_g_rtp_port_remote);
 		send_mncc_rtp_connect();
 	}
 }
@@ -910,10 +924,17 @@ void Pgsm::rtp_connect_ind(unsigned int msg_type, unsigned int callref, struct g
 	struct gsm_mncc_rtp *rtp = (struct gsm_mncc_rtp *) mncc;
 
 	if (p_g_connect_pending) {
+		const struct sockaddr_in *addr;
+
+		addr = reinterpret_cast<const struct sockaddr_in *>(&rtp->addr);
+		assert(addr->sin_family == AF_INET); // XXX
+
 		message = p_g_connect_pending;
-		PDEBUG(DEBUG_GSM, "Got RTP peer info (%08x,%d) forwarding connect\n", rtp->ip, rtp->port);
-		message->param.connectinfo.rtpinfo.ip = rtp->ip;
-		message->param.connectinfo.rtpinfo.port = rtp->port;
+		message->param.connectinfo.rtpinfo.ip = ntohl(addr->sin_addr.s_addr);
+		message->param.connectinfo.rtpinfo.port = ntohs(addr->sin_port);
+		PDEBUG(DEBUG_GSM, "Got RTP peer info (%08x,%d) forwarding connect\n",
+		       message->param.connectinfo.rtpinfo.ip,
+		       message->param.connectinfo.rtpinfo.port);
 		message_put(message);
 		p_g_connect_pending = NULL;
 	}
diff --git a/mncc.h b/mncc.h
index e77ddbd..c823d1e 100644
--- a/mncc.h
+++ b/mncc.h
@@ -1,6 +1,8 @@
 
 #include <stdint.h>
 
+#include <sys/socket.h>
+
 #define MNCC_SETUP_REQ		0x0101
 #define MNCC_SETUP_IND		0x0102
 #define MNCC_SETUP_RSP		0x0103
@@ -85,6 +87,7 @@
 #define MNCC_F_CCCAP		0x0800
 #define MNCC_F_KEYPAD		0x1000
 #define MNCC_F_SIGNAL		0x2000
+#define MNCC_F_GCR		0x4000
 
 /* GSM 04.08 Bearer Capability: Information Transfer Capability */
 enum gsm48_bcap_itcap {
@@ -310,6 +313,12 @@ struct gsm_mncc {
 
 	unsigned char	lchan_type;
 	unsigned char	lchan_mode;
+
+	/* Global Call Reference (encoded as per 3GPP TS 29.205) */
+	uint8_t		gcr[16];
+
+	/* A buffer to contain SDP ('\0' terminated) */
+	char		sdp[1024];
 };
 
 struct gsm_data_frame {
@@ -321,14 +330,14 @@ struct gsm_data_frame {
 struct gsm_mncc_rtp {
 	u_int32_t	msg_type;
 	u_int32_t	callref;
-	u_int32_t	ip;
-	u_int16_t	port;
+	struct sockaddr_storage addr;
 	u_int32_t	payload_type;
 	u_int32_t	payload_msg_type;
+	char		sdp[1024];
 };
 
 
-#define MNCC_SOCK_VERSION	5
+#define MNCC_SOCK_VERSION	8
 struct gsm_mncc_hello {
 	uint32_t	msg_type;
 	uint32_t	version;