What is the purpose of a heartbeat or keep-alive message in the EPD Pilot?

• A. To verify that the connection is still active and to prevent idle timeouts; it helps detect broken links early.
• B. To transfer telemetry data to a central server.
• C. To renegotiate session keys for encryption.
• D. To request a retransmission of a specific frame.

Answer: (A)

Heartbeat messages are there to keep the connection alive and prove the other end is still reachable. They’re small, periodic probes that check the peer’s responsiveness, so if a response isn’t received within a set window, the link is suspected to be down and the session can be closed or re-established quickly. This also helps maintain state through NATs and firewalls that drop idle connections, preventing unnecessary timeouts.

This isn’t about sending telemetry data, which happens with regular data messages. It isn’t about renegotiating encryption keys, which is a security operation separate from liveness checks. And it isn’t about requesting a retransmission of a particular frame, which is part of the data reliability mechanism.