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Re: Is the ability to disable flow control really needed?

From: Martin Thomson <martin.thomson@gmail.com>
Date: Fri, 21 Jun 2013 15:49:48 -0700
Message-ID: <CABkgnnXmgpCfquMhjZofJi+ZmCFDORYk-+HQX+sEU-7WChW=5Q@mail.gmail.com>
To: Fred Akalin <akalin@google.com>
Cc: HTTP Working Group <ietf-http-wg@w3.org>
On 21 June 2013 14:58, Fred Akalin <akalin@google.com> wrote:
> Reading the "Ending Flow Control" section of the spec (3.8.9.4:
> http://http2.github.io/http2-spec/#EndFlowControl ), I'm wondering if we
> even need the ability to disable flow control at all.

This is something that we discussed at some length in the Tokyo
interim.  Getting flow control right is hard.  An implementation will
screw itself if it doesn't take a great deal of care.  Flow control
always costs in performance, at best it just costs the bytes for a few
WINDOW_UPDATE frames; at worst, you end up with lots of periods where
you receive nothing but silence.  Of course, the upside is that you
can get good concurrency without spending infinite amounts of RAM.

This is why we included Section 3.6.2:

http://http2.github.io/http2-spec/#rfc.section.3.6.2

Many simple implementations will choose to avoid flow control.  In
fact, we want to encourage them to avoid implementing it.
Received on Friday, 21 June 2013 22:50:15 UTC

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