Flow control: Backoff

• Link drops excess traffic and signals 'trouble' to the sender

  • Either explicitly or
  • By failing to return an acknowledgment

• Sender responds by waiting for a while and then re-transmitting

• Exponential backoff

  • The sender increases the wait by some factor after every trouble signal and decreases it with each trouble-free send

• Binary exponential backoff

  • The factor is 2
  • It is used in the Ethernet and in TCP

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