Hi,
Just to announce that a wiki page has been created - http://bb.osmocom.org/trac/wiki/dct3-gsmtap and the code is available in the osmocom git repo.
Great, and thanks for writing this, I'm sure easily tracing a real phone exchanges (including SIM exchanges it seems) with some hardware as common as a 3310 will prove useful.
Cheers,
Sylvain