Re: [quicwg/base-drafts] Samples for RTT estimation (#2067)

[janaiyengar <[e-mail]>]

For context, the entire paragraph is:
```
   For fairly modest congestion window sizes, research suggests that
   timing each segment does not lead to a better RTT estimator [AP99].
   Additionally, when multiple samples are taken per RTT, the alpha and
   beta defined in Section 2 may keep an inadequate RTT history.  A
   method for changing these constants is currently an open research
   question.
```

It is true that counting each packet causes us to retire history faster.  Where this matters is when the sender might RTO or TLP too soon, since too late is usually not a problem. This might happen still, but our deployment experience so far has not shown this to cause any undue issues. Specifically, a QUIC sender detects and handles spurious timeouts better than TCP senders did when RFC 2988 (the precursor to RFC 6298) was written.

It may be possible to tweak these constants to make them better for the "correct" timescale, but as @ianswett (and RFC 6298) points out, that is very much open research issue. The numbers in 6298 come from 2988 which was based on measurement studies from 1999 (the end-to-end path properties in the refs section of 6298).

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