coordinationCounterProposal

Operation to forward a counter proposal from the accepting unit to the transferring one or vice versa during the coordination phase.
This is basically replicating the CDN message, but the application context is extended beyond the OLDI scope in order to possibly support counter proposal from transferring to accepting when sent to another sector of the same ATSU.
Counter-proposal input is accepted only if no counter-proposal has been issued before.
The input shall contain the identification of the SFPL, of downstream the responsibility of the transition on which the coordination dialogue was initiated and at least one of the following proposed coordination data: Transfer Flight Level, Route (including direct to a new point), Next SSR code, COP, Time on transition point..