Re: [quicwg/base-drafts] Add a section on flow control performance (#3793)

[ianswett <[e-mail]>]

@ianswett commented on this pull request.



> +order of the current BDP will have receive throughput limited by flow control
+and not other limiting factors like congestion control.  Timely sending of

Congestion controllers sometimes do silly things, so I'd simplify this, but add an additional consideration.

```suggestion
order of the current BDP will have receive throughput limited by flow control.
Lost packets can cause gaps in the receive buffer, delaying the application
from consuming data and freeing up flow control window. Timely sending of
```

> +updates to flow control limits can improve performance. However, an excessive
+rate of updates can also adversely affect performance.

```suggestion
updates to flow control limits can improve performance. An excessive
rate of updates sent in their own packet increases network load and
can adversely affect performance.  Bundling updates with ACK
frames provides frequent updates without adding significant load.
```

> @@ -968,6 +968,17 @@ signal before advertising additional credit, since doing so will mean that the
 peer will be blocked for at least an entire round trip, and potentially for
 longer if the peer chooses to not send STREAMS_BLOCKED frames.
 
+## Flow Control Performance
+
+An endpoint that is unable to ensure that a peer has flow control credit on the
+order of the current BDP will have receive throughput limited by flow control
+and not other limiting factors like congestion control.  Timely sending of
+updates to flow control limits can improve performance. However, an excessive
+rate of updates can also adversely affect performance.
+
+This document does not specify techniques for tuning flow control performance

I don't think this paragraph is necessary, but that's me.

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