On Tue, Jan 10, 2023, at 02:14, Kevin Grigorenko wrote: > Hi, I'm looking into enhancing the Wireshark HTTP2 dissector to track > the connection and session window sizes to investigate flow control > bottlenecks. I have a question about RFC9113 ยง6.9.2: > > "When an HTTP/2 connection is first established, new streams are > created with an initial flow-control window size of 65,535 octets. The > connection flow-control window is also 65,535 octets. Both endpoints > can adjust the initial window size for new streams by including a value > for SETTINGS_INITIAL_WINDOW_SIZE in the SETTINGS frame. The connection > flow-control window can only be changed using WINDOW_UPDATE frames." > > Does the last sentence mean that the connection flow-control window > size can only be changed using a WINDOW_UPDATE frame _after_ the > SETTINGS_INITIAL_WINDOW_SIZE? Not quite. SETTINGS_INITIAL_WINDOW_SIZE governs the initial window for streams, not the connection as a whole. See https://datatracker.ietf.org/doc/html/rfc9113#SETTINGS_INITIAL_WINDOW_SIZE The text is reiterating that the initial size of the connection-level flow control window cannot be changed with a setting, it can only be changed by sending WINDOW_UPDATE frames.Received on Monday, 9 January 2023 21:38:44 UTC
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