msc {
	bts [label="TRX"], bsc [label="BSC"];

	bts => bsc	[label="TCP Connect (Port 3003, RSL)"];
	bts box bsc	[label="IPA CCM Identification (Port 3003)"];
	|||;

	bts <= bsc	[label="SACCH FILLING (SI5)"];
	...;
	bts <= bsc	[label="SACCH FILLING (SI6)"];
	|||;
	bts => bsc	[label="RF Resource Indication"];
	...;
	bts => bsc	[label="RF Resource Indication"];
	...;
}