Sliding-^Advertised- window size #cheatsheet

See also linux tcp receiver tuning for more details. has real life illustration using wireshark.

  • 1) SWS (sliding window size) = amount of transmitted but unacknowledged bytes, a fluctuating control variable in the sender process, like a fluctuatinginventory level“.
  • 2) AWS = amount of free space on receive buffer
  • … I think these two things are related. The sender adjusts SWS based on the feedback of AWS. SWS should be smaller than AWS always.
  • SWS is a concept; AWS is a TCP header field
  • receive buffer size — is also sometimes referred as window size but perhaps incorrectly
  • receiver/sender — only these players control the AWS, not the intermediate routers etc.
  • Original of “Window” — sliding window
  • too large — large AWS is always set based on large receive buffer
  • too small — underutilized bandwidth. As explained in linux tcp buffer^AWS tuning, high bandwidth connections should use larger AWS.

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