Question: During MAP dialogue establishment, if a MAP-OPEN request with version `n` is refused due to 'application context not supported' or 'potential version incompatibility problem', how does the MAP-User proceed?
Option 1: Abort the signalling procedure and notify the application layer of the failure.
Option 2: Issue a new MAP-OPEN request primitive with a lower version `y` (where 1 <= y < n) to attempt compatibility.
Option 3: Automatically increment the version to `n+1` and retransmit the MAP-OPEN request.
Option 4: Repeat the original MAP-OPEN request with version `n` after a predefined timeout.
Explanation: This is because, as per the version handling principles at dialogue establishment, if a higher version `n` is not supported (indicated by a refusal due to 'application context not supported' or 'potential version incompatibility problem'), the MAP-User attempts compatibility by stepping down to a lower version `y` (where 1 <= y < n) to ensure successful dialogue establishment. This approach facilitates backward compatibility and increases the likelihood of a successful connection.