| Adaptive
Retransmission |
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| n | Jacobson/Karels
Algorithm |
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| n | New
calculation for average RTT |
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| – | Diff
= SampleRTT - EstimatedRTT |
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| – | EstimatedRTT
= EstimatedRTT + ( x Diff) |
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| – | Deviation
= Deviation + (|Diff|- Deviation) |
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| – | where
is a fraction between 0 and 1 |
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| n | Consider
variance when setting timeout value |
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| – | TimeOut
= x EstimatedRTT + x Deviation |
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| – | where
= 1 and = 4 |
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| n | Notes |
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| – | algorithm
only as good as granularity of clock (500ms on Unix) |
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| – | accurate
timeout mechanism important to congestion control |
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