Re: [quicwg/base-drafts] A pacing algorithm (#3630)

[Jana Iyengar <[e-mail]>]

@janaiyengar commented on this pull request.



> +as the one in this document, that rate can be computed by averaging the
+congestion window over the round-trip time. Expressed as a rate in bytes:
+
+~~~
+rate = N * congestion_window / smoothed_rtt
+~~~
+
+Or, expressed as an inter-packet interval:
+
+~~~
+interval = smoothed_rtt * packet_size / congestion_window / N
+~~~
+
+Using a value for N that is small, but greater than 1 (for example, 1.25)
+ensures that short-term variations in round-trip time or scheduler delays don't
+result in not fully utilizing the congestion window.

```suggestion
result in under-utilization of the congestion window.
```

> +as the one in this document, that rate can be computed by averaging the
+congestion window over the round-trip time. Expressed as a rate in bytes:
+
+~~~
+rate = N * congestion_window / smoothed_rtt
+~~~
+
+Or, expressed as an inter-packet interval:
+
+~~~
+interval = smoothed_rtt * packet_size / congestion_window / N
+~~~
+
+Using a value for `N` that is small, but at least 1 (for example, 1.25) ensures
+that short-term variations in round-trip time or scheduler delays don't result
+in not fully utilizing the congestion window.

```suggestion
in under-utilization of the congestion window.
```

> @@ -897,9 +897,28 @@ congestion window, which is recommended to be the minimum of
 max_datagram_size is the current maximum size of a datagram for the connection,
 not including UDP or IP overhead.
 
-As an example of a well-known and publicly available implementation of a flow
-pacer, implementers are referred to the Fair Queue packet scheduler (fq qdisc)
-in Linux (3.11 onwards).
+Endpoints can implement pacing as they choose. A perfectly paced sender spreads

I would propose moving this paragraph up one, and adding this to the start of the previous paragraph: "Practical considerations, such as packetization, scheduling delays, and computational efficiency, can cause a sender to deviate from this rate over time periods that are much shorter than a round-trip time. Sending multiple packets into the network without any delay ..."

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