In addition to using encryption to protect the confidentiality of information transmitted from one location to another. organization need to implement controls designed to minimize the risk of data transmission errors. Whenever the receiving unit detects a data transmission error, it requests the sending unit to retransmit that data. Generally, the system will do this automatically and the user is unaware that it has occurred.Occasionally, the system may not be
able to accomplish automatic retransmissions and the sender must manually retransmit the data. Parity checking and message acknowledgement techniques are two basic types of data transmission controls.