Over reliable (error-free) connections, it is possible to eliminate latency by "pre-acknowledging" the packets, a technique known more generally as "protocol spoofing". This is normally accomplished in the link hardware, notably Telebit modems. The modems, when the option was turned on, would notice the XMODEM header and immediately sent an ACK. This would cause the sending XMODEM program to immediately send the next packet, making the transfer continuous, like an infinite-sized window. The modems also suppress the ACK being sent by the XMODEM software at the far end, thereby freeing up the low-speed return channel.