msc {
	hscale=2;
	msc1[label="osmo-msc"], mncc1[label="MNCC FSM"], pbx[label="MNCC server (osmo-sip-connector)"], mncc2[label="MNCC FSM"], msc2[label="osmo-msc"];

	mncc1 note mncc1 [label="The typical progression of an outgoing call, i.e. a call initiated by osmo-msc, as
		implemented in mncc_fsm.h, mncc_fsm.c"];
	mncc2 note mncc2 [label="The typical progression of an incoming call, i.e. a call initiated by the PBX, as
		implemented in mncc_fsm.h, mncc_fsm.c"];

	mncc1 abox mncc1 [label="MNCC_ST_NOT_STARTED"];
	msc1 rbox msc1 [label="mncc_outgoing_start()"];
	msc1 -> mncc1 [label="MNCC_EV_OUTGOING_START"];

	mncc1 abox mncc1 [label="MNCC_ST_OUTGOING_WAIT_PROCEEDING"];
	mncc1 => pbx [label="MNCC_SETUP_IND
			    \n callref, IMSI, called and calling number"];
	mncc1 <= pbx [label="MNCC_RTP_CREATE
			\n callref"];
	mncc1 rbox mncc1 [label="mncc_rx_rtp_create()"];
	mncc1 => pbx [label="MNCC_RTP_CREATE
			\n callref, RTP IP address and port"];
	mncc1 <= pbx [label="MNCC_CALL_PROC_REQ
			\n callref, RTP IP address and port"];
	mncc1 abox mncc1 [label="MNCC_ST_OUTGOING_WAIT_COMPLETE"];

	msc2 <= pbx [label="MNCC_SETUP_REQ
			\n callref, called and calling number"];
	mncc2 abox mncc2 [label="MNCC_ST_NOT_STARTED"];
	msc2 rbox msc2 [label="mncc_incoming_start()"];
	msc2 -> mncc2 [label="MNCC_EV_INCOMING_START"];
	mncc2 abox mncc2 [label="MNCC_ST_INCOMING_WAIT_COMPLETE"];
	mncc2 => pbx [label="MNCC_CALL_CONF_IND
			\n callref, bearer capabilities, cccap and IMSI"];
	mncc2 <= pbx [label="MNCC_RTP_CREATE
			\n callref"];
	mncc2 rbox mncc2 [label="mncc_rx_rtp_create()"];
	mncc2 => pbx [label="MNCC_RTP_CREATE
			\n callref, RTP IP address and port"];
	mncc2 => pbx [label="MNCC_ALERT_IND
			\n callref"];

	mncc1 <= pbx [label="MNCC_ALERT_REQ
			\n callref and progress"];

	mncc2 => pbx [label="MNCC_SETUP_CNF
			\n callref, imsi and connected number"];
	mncc2 <= pbx [label="MNCC_RTP_CONNECT
			\n callref, RTP IP and port"];
	mncc2 rbox mncc2 [label="mncc_rx_rtp_connect()"];
	mncc2 <= pbx [label="MNCC_SETUP_COMPL_REQ
			\n callref"];
	mncc2 abox mncc2 [label="MNCC_ST_TALKING"];

	mncc1 <= pbx [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()"];
	mncc1 <= pbx [label="MNCC_SETUP_RSP
			\n callref"];
	mncc1 => pbx [label="MNCC_SETUP_COMPL_IND
			\n callref"];
	mncc1 abox mncc1 [label="MNCC_ST_TALKING"];

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

	mncc1 rbox mncc1 [label="mncc_release()"];
	mncc1 => pbx [label="MNCC_DISC_IND
			\n callref and cause"];
	mncc1 abox mncc1 [label="MNCC_ST_WAIT_RELEASE_ACK"];
	mncc1 <= pbx [label="MNCC_REL_REQ
			\n callref and cause"];

	mncc2 <= pbx [label="MNCC_DISC_REQ
			\n callref and cause"];
	mncc2 => pbx [label="MNCC_REL_IND
			\n callref and cause"];
	mncc2 abox mncc2 [label="terminated"];

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