Describe a typical acknowledgment (ACK) mechanism in the EPD Pilot and its purpose.

• A. Receivers never acknowledge receptions.
• B. The sender requires confirmation of receipt; the receiver sends an ACK to confirm delivery and enables flow control and retransmission if missing.
• C. ACK is used to mark the end of the session only.
• D. ACK encrypts the data.

Answer: (B)

Acknowledgments establish reliable data transfer. In the EPD Pilot, when the sender transmits data blocks, the receiver replies with an acknowledgment that confirms what has arrived and indicates the next expected sequence, giving the sender a precise picture of progress. This feedback lets the sender pace its transmissions (flow control) so the receiver isn’t overwhelmed, and it provides a mechanism to recover from loss: if an expected acknowledgment doesn’t arrive in time, the sender knows a block may be missing and can retransmit it. Acknowledgments are often cumulative, acknowledging all data up to a certain point, and can be piggybacked on data sent in the other direction to save overhead. The purpose is to keep delivery reliable, ordered, and efficiently paced.

Choosing not to acknowledge would remove the ability to detect loss; using acknowledgments only to mark session end would ignore ongoing data delivery, and encrypting data is a separate security function not related to confirming receipt.