Support HTTP/2 Dynamic Window Sizing in Kestrel

[amcasey]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

Kestrel specifies a static value for the connection and stream window sizes. We've already had to increase the defaults once.

Describe the solution you'd like

Rather than increasing the defaults again (which consumes more resources and increase the risk of DoS), we should make the window size dynamic, as in HttpClient.

The window size should scale with the bandwidth delay product in order to be able accommodate fast connections with significant latency (e.g. transoceanic).

Additional context

No response

[Tratcher]

Related: #4734

[amcasey]

Note that we don't presently validate Ping payloads. We'll probably want to do that if we start using them to adjust window sizes.

[ladeak]

I would be happy to help - even if not a complete feature, but parts of it.

[amcasey]

@ladeak Thanks for volunteering! We're working on our 10.0 planning now and we'll be in a better position to break down and schedule this work once we've settled on a vision for the release.