In data communications, Flow Controllers is the process of managing the rate of data transmission between two nodes to prevent a fast sender from outrunning a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with data from transmitting node. Flow controllers should be distinguished from congestion control, which is used for controlling the flow of data when congestion has actually occurred. Flow controller mechanisms can be classified by whether or not the receiving node sends feedback to the sending node. Flow controller is important because it is possible for a sending computer to transmit information at a faster rate than the destination computer can receive and process it. This can happen if the receiving computers have a heavy traffic load in comparison to the sending computer, or if the receiving computer has less processing power than the sending computer.