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#436: Enable weight of 0

From: Mark Nottingham <mnot@mnot.net>
Date: Wed, 2 Apr 2014 13:56:34 +1100
Cc: "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
Message-Id: <F76B36B7-1973-4E96-B43C-30D1AA55369E@mnot.net>
To: RUELLAN Herve <Herve.Ruellan@crf.canon.fr>
Hi Herve,

IIRC we discussed this as part of #270 in London:

... and the feeling in the room was that we didn't want to do this.

Does Herve's use case below change people's minds? If not, how do people think he should address it?


On 2 Apr 2014, at 4:10 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.
> This scenario is of importance for Canon, as we would like to be able to download in the background heavy media from a camera, while still retaining the ability to control it in real time. This means that we want to have ways of ensuring that the data used for controlling the camera (which can be somewhat heavy when it includes real-time preview) can take prevalence over the other transfer without delay.
> 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.
> Another scenario is to temporary suspend some groups to allow a more urgent group to take all the bandwidth. This can be useful when opening several webpages at once: only the foreground one has a weight greater than 0, allowing it to be downloaded quickly.
> I understand that including the value of 0 for the weight somewhat increases implementation complexity, but I think the benefits are well worth it.
> Cheers,
> Hervé.

Mark Nottingham   http://www.mnot.net/
Received on Wednesday, 2 April 2014 02:56:57 UTC

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