3.1.1.3 Receipts
SRMP augments the underlying transport by using additional levels of acknowledgment to ensure that messages are reliably transferred, regardless of failures in transport connection, applications, or nodes.
Message receipts provide a mechanism for the receiver to notify the sender whether it received a message, and optionally, whether the message was saved to disk. When the sender receives a receipt, it can discard the acknowledged messages that it stored locally.
The sender retransmits unacknowledged messages if it does not receive a receipt within the specified time-out period. SRMP implements message receipts at both the individual message and transactional sequence layers.