oml interface design notes

problems:

* there is no way how to tag a command sent to the BTS, with the response
  having the same tag to identify the originator of the command
* therefore, we can have e.g. both the BSC and the OML interface send a
  SET ATTRIBUTE message, where the responses would end up at the wrong
  query.
* The BTS has 10s to ACK/NACK a command. We do not run any timers.

the only possible solutions i can imagine:
* have some kind of exclusive locking, where the OML interface gets blocked
  from the BSC and is exclusively assigned to the OML console until all commands
  of the OML console have terminated.  This can either be done explicitly
  dynamically or on demand

* use the OML interface synchronously, i.e. always wait for the response from
  the BTS before

* unilateral / unsolicited messages need to be broadcasted to both the BSC and
  the OML console
