# MO-Call with OsmoBTS + OsmoBSC using A/IP with IPA/SCCPlite
# Supported since 2010 using osmo-bsc + osmo-bsc_nat
msc {
	hscale=2;
	ms [label="MS"], bts [label="OsmoBTS"], bsc[label="OsmoBSC"], mgcp[label="osmo-bsc_mgcp"], m_sc[label="MSC"]; 

	ms box m_sc	[label="We assume a SDCCH is already established"];
	...;

	ms -> m_sc	[label="DTAP CC SETUP"];
	ms <- m_sc	[label="DTAP CC CALL PROCEEDING"];

	bsc <- m_sc 	[label="BSSAP ASSGN REQ"];
	bts <- bsc 	[label="RSL CHAN ACT"];
	bts -> bsc 	[label="RSL CHAN ACT ACK"];
	ms <-> bsc	[label="Assignment"];
	bsc -> m_sc	[label="BSSAP ASSGN CMPL"];

	...;
	bts <- bsc	[label="IPA CRCX"];
	bts box bts	[label="Bind to BSC-local RTP Port"];
	bts -> bsc	[label="IPA CRCX ACK"];
	bts <- bsc	[label="IPA MDCX"];
	bts box bts	[label="Connect RTP socket to remote (bsc_mgcp) RTP Port"];
	bts -> bsc	[label="IPA MDCX ACK"];

	mgcp <- m_sc	[label="MGCP CRCX 1@mgw"];
	mgcp box mgcp	[label="Bind to BTS-local RTP Port"];
	mgcp -> m_sc	[label="MGCP CRCX 1@mgw OK"];
	mgcp <- m_sc	[label="MGCP MDCX 1@mgw (recvonly) "];
	mgcp box mgcp	[label="Connect RTP socket to remote (MSC) RTP Port"];
	mgcp -> m_sc	[label="MGCP MDCX 1@mgw OK"];
	mgcp <= m_sc	[label="RTP Audio"];
	bts <= mgcp	[label="RTP Audio"];
	ms <= bts	[label="Um Audio (unidirectional)"];
	ms <- m_sc	[label="DTAP CC ALERTING"];

	...;
	mgcp <- m_sc	[label="MGCP MDCX (sndrecv) "];
	mgcp box mgcp	[label="Switch to bi-directional audio"];
	mgcp -> m_sc	[label="MGCP MDCX OK"];
	mgcp <=> m_sc	[label="RTP Audio"];
	bts <=> mgcp	[label="RTP Audio"];
	ms <=> bts	[label="Um Audio (bidirectional)"];
	...;
	ms <- m_sc	[label="DTAP CC CONNECT"];
	ms -> m_sc	[label="DTAP CC CONNECT ACK"];
	mgcp <- m_sc	[label="MGCP MDCX 1@mgw (sndrecv) "];
	mgcp box mgcp	[label="Why?"];
	mgcp -> m_sc	[label="MGCP MDCX 1@mgw OK"];
	---		[label="Voice Call in Progress"];
	ms <- m_sc	[label="DTAP CC DISCONNET"];
	ms <- m_sc	[label="DTAP CC RELEASE"];
	ms <- m_sc	[label="DTAP CC RELEASE COMPL"];
	...;
	bsc <- m_sc	[label="BSSMAP CLEAR CMD"];
	bsc -> m_sc	[label="BSSMAP CLEAR COMPL"];
	bsc <- m_sc	[label="SCCP RLSD"];
	bsc -> m_sc	[label="SCCP RLC"];
	...;
	mgcp <- m_sc	[label="MGCP DLCX 1@mgw"];
	mgcp box mgcp	[label="Release local RTP port"];
	mgcp -> m_sc	[label="MGCP DLCX 1@mgw OK"];
}