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Exponential backoff
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===Example=== This example is from the [[Ethernet]] protocol,<ref>{{cite book| title=Computer Networks: A Systems Approach |url=https://book.systemsapproach.org/ |last1=Peterson |first1=Larry L. |last2=Davie |first2=Bruce S. |chapter=Chapter 2: Direct Links | chapter-url=https://book.systemsapproach.org/direct/ethernet.html#transmitter-algorithm |page=120 |publisher=Morgan Kaufmann Publishers |edition=Sixth |year=2022 |isbn=978-0-12-818200-0 }}</ref> where a sending host is able to know when a collision has occurred (that is, another host has tried to transmit), when it is sending a frame. If both hosts attempted to re-transmit as soon as a collision occurred, there would be yet another collision — and the pattern would continue forever. The hosts must choose a random value within an acceptable range to ensure that this situation doesn't happen. An exponential backoff algorithm is therefore used. The value 51.2 μs is used as an example here because it is the [[slot time]] for a {{val|10 |u=Mbit|up=s}} Ethernet line. However, {{val|51.2 |u=μs}} could be replaced by any positive value, in practice. # When a collision first occurs, send a ''jamming signal'' to prevent further data from being sent. # Resend a frame after either 0 seconds or {{val|51.2 |u=μs}}, chosen at random. # If that fails, resend the frame after either {{val|0 |u=s}}, {{val|51.2 |u=μs}}, {{val|102.4 |u=μs}}, or {{val|153.6 |u=μs}}. # If that still fails, resend the frame after {{mvar|k}} · {{val|51.2 |u=μs}}, where {{mvar|k}} is a random integer between 0 and {{math|2<sup>3</sup> − 1}}. # For further failures, after the ''c''th failed attempt, resend the frame after {{mvar|k}} · {{val|51.2 |u=μs}}, where {{mvar|k}} is a random integer between 0 and {{math|2<sup>''c''</sup> − 1}}.
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