[GitHub] [trafficserver] maskit commented on pull request #9085: Make HTTP/2 session and stream windows configurable

[GitBox <gi...@apache.org>]

maskit commented on PR #9085:
URL: https://github.com/apache/trafficserver/pull/9085#issuecomment-1243098660

   Like I said on #8199, this change doesn't make sense to me. Just setting a large number to connection window size is effectively removing flow control for a connection. And even if you can set a reasonable value to connection window size, setting stream window size separately by hand isn't great because you need to estimate the average number of streams on a connection before hand. Let's say connection window size is 256KB. If the average number of streams is 2, stream window size should be 256 / 2 = 128KB. This stream window size is not the best for a connection that has just one stream (one stream can't fully utilize the connection).
   
   My suggestion is:
   - Keep `proxy.config.http2.initial_window_size_in` as the only setting for H2 window size
   - Set the initial connection window size to `proxy.config.http2.initial_window_size_in * proxy.config.http2.max_concurrent_streams_in` at the beginning of a connection
   - Send SETTINGS frame with the value of `the-connection-window-size / #-of-open-streams` when the number of open streams changes (or alternatively, send WINDOW_UPDATE on each stream)
   
   You can set initial connection window size by adjusting initial_window_size_in (for stream) and max_concurrent_streams_in. This should work for you since you'd have a larger connection window size while you keep your initial stream window size as is. The last item is optional but it's to fully utilize a connection by a low number of streams and I think we should do this. 
   


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