What Does Backpressure Mean?

Backpressure refers to the buildup of data at an I/O switch when buffers are full and not able to receive additional data. No additional data packets are transferred until the bottleneck of data has been eliminated or the buffer has been emptied.


Techopedia Explains Backpressure

To create backpressure, the I/O switch must broadcast false collision detection signals or return data packets to their originator.

Protocols are written to deal with such conditions at a node, in this case at a switch. For example, Ethernet uses carrier sense multiple access/collision detection (CSMA/CD). This is an internationally standardized protocol called a contention protocol, which determines how network devices respond to backpressure. It also determines when two devices attempt to use the same channel (a signal medium such as a wire or fiber optic cable) simultaneously without being multiplexed. CSMA/CD is standardized in IEEE 802.3 and ISO 8802.3.

All participating stations detect the backpressure or data packet collisions. After a predetermined time interval, the transmitting stations will again attempt to transmit. If the collisions are again detected, the time interval before data transmission is increased, and then increased incrementally each time the problem is detected. This process is called exponential back-off.


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Margaret Rouse

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.