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andydavies / http2-prioritization-issues

Tracks issues / notes for HTTP/2 prioritization across browsers, CDNs and servers
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support for HTTP/2 PRIORITY_UPDATE instead of HTTP/2 PRIORITY ? #22

Open gstrauss opened 1 year ago

gstrauss commented 1 year ago

Is there a table for support for HTTP/2 PRIORITY_UPDATE instead of HTTP/2 PRIORITY ?

RFC 9113 HTTP/2 5.3.2. Priority Signaling in This Document deprecates HTTP/2 PRIORITY frame.

The suggested replacement for PRIORITY frame is the PRIORITY_UPDATE frame. RFC 9218 Extensible Prioritization Scheme for HTTP

pmeenan commented 1 year ago

The test doesn't care how the priority is set, just that the origin supports whatever the browser uses. i.e. it should work out-of-the-box for HTTP/3 with no changes.

That said, the test could probably use an update to explicitly set fetchpriority=low for the offscreen images and fetchpriority=high for the on-screen test images so that the initial priority is correct and it doesn't require an update.

gstrauss commented 1 year ago

Thanks! I suppose this can be closed.

Modern browsers should support PRIORITY_UPDATE, though middle boxes might not yet support HTTP/2 SETTINGS_NO_RFC7540_PRIORITIES.

I know you wrote https://blog.cloudflare.com/http-2-prioritization-with-nginx/ back in 2018. Hopefully, support for prioritization in origin web servers has improved with PRIORITY_UPDATE (RFC 9218 published June 2022). I added PRIORITY_UPDATE support to lighttpd 1.4.65 (released June 2022).

The Servers section of https://github.com/andydavies/http2-prioritization-issues appears to be a pending TODO.