data link devices (send/recv raw packet) (better called LLC devices?)
  iso uart (iso9141 interface)
  sw bit banging devices (serial) (saej1850 interface)
  (IP encapsulation)
  (proprietary stuff)
network driver (addressing) (data link MAC?)
  obd2 over data link (j1850, j2178)
  iso9141
  iso14230
  obd2 over iso9141 (iso9141, j1850)
  obd2 over iso14230
transport (or network, if above is data link MAC?)
  diag modes, enhanced diag modes
  message formats
presentation
  security
  prn/slot
application
  scan tool