msc {
	hscale=3;
	msc1[label="osmo-msc"], mncc1[label="MNCC FSM\n(osmo-msc mncc_call.c)"], sipcon1[label="osmo-sip-connector"], sip[label="PBX"], sipcon2[label="osmo-sip-connector"], mncc2[label="MNCC FSM\n(osmo-msc mncc_call.c)"], msc2[label="osmo-msc"];

	msc1 note sipcon1 [label="MO call"];
	sipcon2 note msc2 [label="MT call"];

	mncc1 abox mncc1 [label="MNCC_CALL_ST_NOT_STARTED"];
	msc1 rbox msc1 [label="mncc_outgoing_start()"];
	msc1 -> mncc1 [label="MNCC_CALL_EV_OUTGOING_START"];

	mncc1 abox mncc1 [label="MNCC_CALL_ST_OUTGOING_WAIT_PROCEEDING"];
	mncc1 => sipcon1 [label="MNCC_SETUP_IND
			    \n callref, IMSI, called and calling number, SDP"];
	sipcon1 => sip [label="SIP INVITE
			\n from, to, SDP"];
	sipcon1 <= sip [label="SIP 100 Trying"];
	mncc1 <= sipcon1 [label="MNCC_RTP_CREATE
			\n callref"];
	mncc1 rbox mncc1 [label="mncc_rx_rtp_create()"];
	mncc1 => sipcon1 [label="MNCC_RTP_CREATE
			\n callref, RTP IP address and port"];
	mncc1 <= sipcon1 [label="MNCC_CALL_PROC_REQ
			\n callref, RTP IP address and port"];
	mncc1 abox mncc1 [label="MNCC_CALL_ST_OUTGOING_WAIT_COMPLETE"];

	sip => sipcon2 [label="SIP INVITE
			\n from, to, SDP"];
	sipcon2 => sip [label="SIP 100 Trying"];
	msc2 <= sipcon2 [label="MNCC_SETUP_REQ
			\n callref, called and calling number
			\n SDP"];
	mncc2 abox mncc2 [label="MNCC_CALL_ST_NOT_STARTED"];
	msc2 rbox msc2 [label="mncc_incoming_start()"];
	msc2 -> mncc2 [label="MNCC_CALL_EV_INCOMING_START"];
	mncc2 abox mncc2 [label="MNCC_CALL_ST_INCOMING_WAIT_COMPLETE"];
	mncc2 => sipcon2 [label="MNCC_CALL_CONF_IND
			\n callref, bearer capabilities, cccap and IMSI, SDP?"];
	mncc2 <= sipcon2 [label="MNCC_RTP_CREATE
			\n callref"];
	mncc2 rbox mncc2 [label="mncc_rx_rtp_create()"];
	mncc2 => sipcon2 [label="MNCC_RTP_CREATE
			\n callref, RTP IP address and port, SDP?"];
	mncc2 => sipcon2 [label="MNCC_ALERT_IND
			\n callref"];
	sipcon2 => sip [label="SIP 180 Ringing
			\n SDP"];

	sipcon1 <= sip [label="SIP 180 Ringing
			\n SDP"];
	mncc1 <= sipcon1 [label="MNCC_ALERT_REQ
			\n callref and progress"];
	sipcon1 => sip [label="SIP PRACK 180 Ringing"];
	sipcon1 <= sip [label="SIP PRACK 200"];

	mncc1 <= sipcon1 [label="MNCC_RTP_CONNECT
			\n callref, RTP IP and port"];
	mncc1 rbox mncc1 [label="mncc_rx_rtp_connect()"];
	msc1 <- mncc1 [label="rtp_stream_set_remote_addr()"];

	mncc2 => sipcon2 [label="MNCC_SETUP_CNF
			\n callref, imsi and connected number, SDP?"];
	sipcon2 => sip [label="SIP 200 OK
			\n SDP"];
	mncc2 <= sipcon2 [label="MNCC_RTP_CONNECT
			\n callref, RTP IP and port"];
	mncc2 rbox mncc2 [label="mncc_rx_rtp_connect()"];
	mncc2 <= sipcon2 [label="MNCC_SETUP_COMPL_REQ
			\n callref"];
	mncc2 abox mncc2 [label="MNCC_CALL_ST_TALKING"];

	sipcon1 <= sip [label="SIP 200 OK INVITE"];
	mncc1 <= sipcon1 [label="MNCC_SETUP_RSP
			\n callref"];
	mncc1 => sipcon1 [label="MNCC_SETUP_COMPL_IND
			\n callref"];
	mncc1 abox mncc1 [label="MNCC_CALL_ST_TALKING"];
	sipcon1 => sip [label="SIP ACK"];

	...;
	... [label="Call goes on for a while..."];
	...;

	mncc1 rbox mncc1 [label="mncc_release()"];
	mncc1 => sipcon1 [label="MNCC_DISC_IND
			\n callref and cause"];
	mncc1 abox mncc1 [label="MNCC_CALL_ST_WAIT_RELEASE_ACK"];
	sipcon1 => sip [label="SIP BYE"];
	sipcon1 <= sip [label="SIP 200 OK"];
	mncc1 <= sipcon1 [label="MNCC_REL_REQ
			\n callref and cause"];

	sip => sipcon2 [label="SIP BYE"];
	sip <= sipcon2 [label="SIP 200 OK"];
	mncc2 <= sipcon2 [label="MNCC_DISC_REQ
			\n callref and cause"];
	mncc2 => sipcon2 [label="MNCC_REL_IND
			\n callref and cause"];
	mncc2 abox mncc2 [label="terminated"];

	mncc1 => sipcon1 [label="MNCC_REL_CNF
			\n callref"];
	mncc1 abox mncc1 [label="terminated"];
}