Re: [quicwg/base-drafts] HTTP/3 with strict priorities (#2700)

Robin Marx <notifications@github.com> Thu, 23 May 2019 07:41 UTC

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Subject: Re: [quicwg/base-drafts] HTTP/3 with strict priorities (#2700)
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Just to come back to my comment from before:

> It would also allow resolving #2690 in the same way as proposed in #2723 : just make priority 0, no weight the default for new nodes!

This is not entirely correct sadly... 
Main example is Safari/Edge behaviour: all nodes dependent on the root, setting explicit weights (but no priorities!).

If un-prioritized/default nodes are added with priority 0 + weight 0, they would share the bandwidth 50/50 with the weighted nodes, making this default even worse than the HTTP/2 of adding the nodes with weight 16... 

Potential solution is to add them with priority=0,weight=1, but then they will still get some part of the bandwidth (how much depends on the weights of other things) and we are again back to round-robin (which we don't want, we want FIFO in the default case). 

So, other solutions:
- Nodes without priorities and without weights (default): priority=0, weight=0. Nodes without priorities but WITH weights (explicit behaviour): priority=1,weight=incoming
- Special priority level -1 ("implicit orphan placeholder")
- Explicit orphan placeholder (#2690) (BUT then we can't implement this setup without any placeholders at all, which is possible at the moment)

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