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