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Re: Enable weight of 0

From: David Krauss <potswa@gmail.com>
Date: Wed, 2 Apr 2014 03:19:04 +0800
Message-Id: <72B846A6-EDB6-46EE-AF38-E7FB92DB664F@gmail.com>
To: HTTP Working Group <ietf-http-wg@w3.org>

On 20140402, at 1:10 AM, RUELLAN Herve <Herve.Ruellan@crf.canon.fr> wrote:

> I think we should change the range of weights for a group from 1-256 to 0-255.
> 
> The meaning of the weight 0 is to indicate that no resource should be allocated to the priority group, unless there are available resources that can't be used by any priority group with a weight greater than 0.
> 
> This new weight would help better handling several scenarios.
> 
> First, the downloads from a website could be put in a group with a weight of 0: they would not impede the user's navigation inside the website, taking advantage of the network idle time when the user is reading a page.

Would it not be a compliant extension for the server to apply such semantics to a weight of 1? The precision of resource allocation is an implementation detail.

> This scenario could be handled by using flow control, but this result in some added latency: at least 1 RTT would elapse between a server finishing to send the data corresponding to a webpage and the server receiving the window update unblocking the flow control for the downloads. The same holds when starting to transfer a webpage content. In addition, this would create interdependencies between priorities and flow control.

Yes, I agree completely. Its a slow way to communicate what should be a timely message. Proxies and balancers need to try to tolerate what would otherwise be misbehavior.

Also, if semantically meaningful underflow is eliminated, the flow control scheme overhead may be cut in half and its complexity reduced accordingly.
Received on Tuesday, 1 April 2014 19:20:35 UTC

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