RTT Measurement of TCP

• Impact of RTT-gain coefficient

  • Acts as „smoothing“ factor
  • Considered values
    • gain = 0.125
    • gain = 1

• Results

  • Derivation less than 1ms
  • „Smoothed“ curved closerto real round-trip delayvariation

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Graphik-Version anzeigen

Simulator Settings:
timer granularity: none

min. RTT valu: 1ms

==> smoothed timer gives better approximation of RTT variation

Annotation:

==> still suboptimal estimation of „real“ RTT due to TCP contrains
transmission window experinces havy changes

<=> needless retransmissions due to low timer granularity

queuing delay adds a constant offset of approx. 38ms

Inlcude later:
picture of queuing delay & transmission window size

can we reduce the queuing delay with very hight speed link
==> should only work if BDP is larger than window size