[tor-commits] [torspec] 02/04: Prop 324: Document new `cc_ewma_ss` consensus parameter.

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commit 07c731e8362ef0b9d47a227249366afe38261bbf
Author: Mike Perry <mikeperry-git at torproject.org>
AuthorDate: Wed Aug 10 22:13:38 2022 +0000

    Prop 324: Document new `cc_ewma_ss` consensus parameter.
---
 proposals/324-rtt-congestion-control.txt | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/proposals/324-rtt-congestion-control.txt b/proposals/324-rtt-congestion-control.txt
index 78d526d..0e8c349 100644
--- a/proposals/324-rtt-congestion-control.txt
+++ b/proposals/324-rtt-congestion-control.txt
@@ -169,10 +169,12 @@ Moving Average with alpha = 2/(N+1):
 
   N_EWMA = BDP*2/(N+1) + N_EWMA_prev*(N-1)/(N+1).
 
-Flow control rate limiting uses this function
+Flow control rate limiting uses this function.
 
-For both RTT and SENDME BDP estimation, N is the number of SENDME acks
-between congestion window updates, divided by the value of consensus
+During Slow Start, N is set to `cc_ewma_ss`, for RTT estimation.
+
+After Slow Start, for both RTT and SENDME BDP estimation, N is the number
+of SENDME acks between congestion window updates, divided by the value of consensus
 parameter 'cc_ewma_cwnd_pct', and then capped at a max of 'cc_ewma_max',
 but always at least 2:
 
@@ -1293,6 +1295,15 @@ These are sorted in order of importance to tune, most important first.
            congestion, to avoid overloading slow relays. Values of 10 or 20
            were best.
 
+  cc_ewma_ss:
+    - Description: This specifies the N in N_EWMA smoothing of RTT during
+                   Slow Start.
+    - Range: [2, INT32_MAX]
+    - Default: 2
+    - Tuning Values: [2,4]
+    - Shadow Tuning Results:
+           Setting this to 2 helped reduce overshoot during Slow Start.
+
   cc_cwnd_inc:
     - Description: How much to increment the congestion window by during
                    steady state, every cwnd.

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