private void applyResponseAcknowledgement(
            final Builder builder,
            final long rid) {
        assertLocked();

        if (responseAck.equals(Long.valueOf(-1L))) {
            // We have not received any responses yet
            return;
        }

        Long prevRID = Long.valueOf(rid - 1L);
        if (responseAck.equals(prevRID)) {
            // Implicit ack
            return;
        }
        
        builder.setAttribute(Attributes.ACK, responseAck.toString());
    }