Truncated binary exponential backoff: Difference between revisions

Revision as of 09:12, 20 December 2006

Revision as of 08:00, 2 February 2007

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In a variety of [[computer networks]], '''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]].

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 retransmissionretransmissions after a collision is thatcollisions. theThe 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. So, 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.