What is flow control

Improve Article. Like Article. Last Updated : 08 Sep, Previous Methods of Line Discipline. Recommended Articles. Article Contributed By :. Easy Normal Medium Hard Expert. Writing code in comment? Please use ide. Load Comments. As we saw that the disadvantage of the stop and wait protocol is that the sender waits for the acknowledgment and during that time the sender is idle. In sliding window protocol we will utilize this time.

We will change this waiting time into transmission time. A window is a buffer where we store the frames. Each frame in a window is numbered. If the window size is n then the frames are numbered from the number 0 to n A sender can send n frames at a time.

When the receiver sends the acknowledgment of the frame then we need not store that frame in our window as it has already been received by the receiver. So, the window in the sender side slides to the next frame and this window will now contain a new frame along with all the previous unacknowledged frames of the window. At any instance of time window will only contain the unacknowledged frames. This can be understood with the example below:. Using sliding window protocol, the efficiency can be made maximum i.

In sliding window protocol we are using the propagation delay time also for the transmission. For doing this we the sender should be sending the data frame all the time i. So, what should be the number of packets such that the efficiency is maximum? We will apply a simple unitary method to find this.

In Td units of time, we can send one packet. This is how the flow of data is controlled using the above two mechanisms. Filters 0. It provides notification to the sending device to slow down or speed up data transmission or data transfer due to the receiving device's current ability to keep up with it. Flow control also enables slower-speed devices to communicate with higher-speed ones and vice versa. See xon-xoff. The process of controlling the rate of data transfer in order to prevent data loss due to congestion, flow control is an element of many data communications protocols.

Between a PC and a local printer, for example, there is a simple flow control mechanism that throttles back the data transfer rate from the PC to ensure that the printer is not overwhelmed and that the printer buffer memory is not exceeded.