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In a variety of#REDIRECT [[computerExponential networks]], '''binarybackoff#Binary exponential backoff''' or/ '''truncated binary exponential backoff''' refers to an [[algorithm]] used to space out repeated [[retransmission (data networks)|retransmissions]] of the same block of [[data]].
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Examples are the retransmission of [[data frame|frames]] in [[carrier sense multiple access with collision avoidance]] (CSMA/CA) and [[carrier sense multiple access with collision detection]] (CSMA/CD) networks, where this algorithm is part of the channel access method used to send data on these network. In [[Ethernet]] networks, the algorithm is commonly used to schedule retransmissions after collisions. The retransmission is delayed by an amount of [[time]] derived from the [[slot time]] and the number of attempts to retransmit.
After i collisions, a random number of slot times between 0 and <math>2^i-1</math> is chosen. For the first collision, each sender might wait 0 or 1 slot times. After the second collision, the senders might wait 0, 1, 2, or 3 slot times, and so forth. As the number of retransmission attempts increases, the number of possibilities for delay increases.
The 'truncated' simply means that after a certain number of increases, the exponentiation stops; i.e. the retransmission timeout reaches a ceiling, and thereafter does not increase any further. For example, if the ceiling is set at i=10, then the maximum delay is 1023 slot times.
Because these delays cause other stations who are sending to collide as well, there is a possibility that, on a busy network, hundreds of people may be caught in a single collision set. Because of this possibility, after 16 attempts at transmission, the process is aborted.
==See also==
*[[Exponential backoff]]
==References==
*{{FS1037C}}
[[Category:Networking algorithms]]
[[Category:Ethernet]]
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[[de:Binary Exponential Backoff]]
[[fr:Binary Exponential Backoff]]
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