Retransmission

In an packet switching communication network, retransmission is the process of re-sending data or packets which were damaged or lost by the basic network, and for which therefore no acknowledgement was received before a timeout after it was originally sent.

If a given data item/packet is retransmitted a number of times, and no acknowledgement for it is ever received, that generally means that either the host on the other end has crashed, or there is a fault in the network which means packets cannot be exchanged between the two ends, and the connection is usually aborted.