We assume in the following discussion that the network deals with routing issues, and the like. IP does not allow this selective retransmission. If a single fragment does not arrive or is corrupted, the entire message must be resent. Doesn't guarantee message delivery. If the receiver does not receive the first fragment, then the receiver does nothing, and the sender times-out.
Receiver gives up.
An exception may be thrown to the receiving and sending parties. Total number of fragments to be sent. We discussed the necessity of being careful about the MID number wrapping. Since both messages have the same MID, the receiver will not know to which message it should ascribe the fragments. We require a new MID every 1 us. 6 million MIDs in 60s.