When requested, this VDE Protocol Format may be used by an application to confirm the reception and processing of a VDES addressed specific application message. An application should never acknowledge a broadcast message. Manual acknowledgement by human interaction is not covered by this mechanism.
If the interrogating application does not receive this acknowledgment reply, even though it was requested, then the application should assume that addressed VDE protocol format is not handled by the interrogated station.
The interrogated protocol format handling application shall respond with this message within 1 second after receiving the addressed interrogation message.
IALA
G1117-Ed3.0-VHF-Data-Exchange-System-VDES-Overview