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commit d339bb9fab10c32c10fce0e06421bbadaffe2777 Author: Mike Perry mikeperry-git@torproject.org AuthorDate: Wed Aug 10 22:28:33 2022 +0000
Prop 324: Describe how to reset RTT if cc_cwnd_min is hit. --- proposals/324-rtt-congestion-control.txt | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
diff --git a/proposals/324-rtt-congestion-control.txt b/proposals/324-rtt-congestion-control.txt index 0e8c349..c9997ef 100644 --- a/proposals/324-rtt-congestion-control.txt +++ b/proposals/324-rtt-congestion-control.txt @@ -389,6 +389,13 @@ Simplifying:
BDP = cwnd * RTT_min / RTT_current_ewma
+The RTT_min for this calculation comes from the minimum RTT_current_ewma +seen in the lifetime of this circuit. If the congestion window falls to +`cc_cwnd_min`, implementations MAY choose to reset RTT_min for use in this +calculation to either the RTT_current_ewma, or a percentile-weighted average +between RTT_min and RTT_current_ewma, specified by `cc_rtt_reset_pct`. This +helps with escaping starvation conditions. + The net effect of this estimation is to correct for any overshoot of the cwnd over the actual BDP. It will obviously underestimate BDP if cwnd is below BDP. @@ -1304,6 +1311,16 @@ These are sorted in order of importance to tune, most important first. - Shadow Tuning Results: Setting this to 2 helped reduce overshoot during Slow Start.
+ cc_rtt_reset_pct: + - Description: Describes a percentile average between RTT_min and + RTT_current_ewma, for use to reset RTT_min, when the + congestion window hits cwnd_min. + - Range: [0, 100] + - Default: 100 + - Shadow Tuning Results: + cwnd_min is not hit in Shadow simulations, but it can be hit + on the live network while under DoS conditions, and with cheaters. + cc_cwnd_inc: - Description: How much to increment the congestion window by during steady state, every cwnd.