Describe any circumstances under which an open-loop protocol eg a Hamming code might be preferable to the feedback-type protocols.?

If the propagation delay is very long, as in the case of a space probe on or near Mars or Venus, forward error correction is indicated. It is also appropriate, in a military situation in which the receiver does not want to disclose his location by transmitting. If the error rate is low enough that an errorcorrecting code is good enough, it may also be simpler. Finally, real-time systems cannot tolerate waiting for retransmissions.