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Re: proposed WINDOW_UPDATE text for session flow control windows

From: Patrick McManus <mcmanus@ducksong.com>
Date: Tue, 12 Feb 2013 09:54:21 -0500
Message-ID: <CAOdDvNqTNa=R1MzZe1mKZF34tW-=mhHnM_s_XPVzBBSEWHveVQ@mail.gmail.com>
To: William Chan (陈智昌) <willchan@chromium.org>
Cc: HTTP Working Group <ietf-http-wg@w3.org>
On Sun, Feb 10, 2013 at 2:14 PM, William Chan (陈智昌)

> Do servers often have a need to immediately revoke buffer size promises?
> In absence of negative window updates, I would think servers would just
> stop sending WINDOW_UPDATEs. Is that mechanism insufficient?

In this case I was thinking about firefox. In general we don't have a ram
budget for transactions in the way a server does, so the reasonable thing
to do in the general case is to set flow control to a very high value to
ensure it isn't a choke point, right? However, RAM does have a way of
suddenly appearing to be low and we get notifications of that. Lots of
times this is due to other unrelated system activity - this is especially
true on mobile. Currently we do a handful of things in reaction to that
(dumping decoded image caches for example). Another reasonable reaction to
that is to squelch some active streams and shrink their associated
buffers.. this is the context I was thinking about.

waiting for a very large window to drain via lack-of-updates could take an
extremely long time.

> All in all, I don't feel very strongly on this. I'd rather hear from more
> proxy/server vendors that they want this, rather than adding it in just
> because it might be useful. Or are you suggesting that Firefox would like
> to use this?
Received on Tuesday, 12 February 2013 14:54:53 UTC

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