Re: [quicwg/base-drafts] allow PRIORITY frames referring to placeholders exceeding `SETTING_NUM_PLACEHOLDERS` (#2761)

Robin Marx <> Wed, 05 June 2019 09:19 UTC

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Date: Wed, 05 Jun 2019 09:18:57 +0000
From: Robin Marx <>
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Subject: Re: [quicwg/base-drafts] allow PRIORITY frames referring to placeholders exceeding `SETTING_NUM_PLACEHOLDERS` (#2761)
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> Yeah. I think that the anticipation behind this PR is that a server would either support no placeholders at all, or be capable of handling enough number of placeholders. FWIW, Firefox uses 4 "placeholders" in HTTP/2. I do not think that there would be a reason for a HTTP/3 with support for placeholders to support something below 4.

@kazuho do you have a source for this? afaik, it uses 6...

I agree that current browser approaches do not require many placeholders, but as also included in Ian's presentation in London, if you want to simulate something like @patmeenan's scheme with placeholders, you need 4 placeholders per priority-level (of which that scheme uses a default of 3, so 12 placeholders minimum total). 

I share's @ghedo's views that making this an advisory SETTING would not mean much in practice if not coupled with a minimum amount of placeholders servers MUST support. I'm more for requiring at least X placeholders (X > 32 in my opinion).

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