Data that is not part of the user data, but that is stored or transmitted with it. Overhead can be used for a wide variety of purposes, such as circuit monitoring, channel separation, addressing, error control, priority indication, and congestion management. Although overhead is essential to the integrity of data storage and transmission, it reduces the amount of user data that can be stored or transmitted. In a circuit or channel used to maximum capacity, bandwidth less overhead equals throughput. See also bandwidth and throughput.