I hope this finds you all in the best of health. As a start, I have read some basic GSM articles and went through bsc_hack.c.  Few questions are bugging me and I would appreciate some info regarding them:

(1) With which type(s) of BTS does OpenBSC work?

(2) What is OML NM?

(3) What is the best way to follow the path in the code in case of a call?

Thanks.