From: Hagen Paul Pfeifer <hagen@jauu.net>
To: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
Dave Taht <dave.taht@gmail.com>,
Stephen Hemminger <shemminger@vyatta.com>,
Thomas Graf <tgraf@infradead.org>,
netdev <netdev@vger.kernel.org>, Jim Gettys <jg@freedesktop.org>
Subject: Re: [PATCH] sch_red: fix red_change
Date: Wed, 7 Dec 2011 23:57:48 +0100 [thread overview]
Message-ID: <20111207225747.GA4758@nuttenaction> (raw)
In-Reply-To: <alpine.DEB.2.00.1112051221510.31705@wel-95.cs.helsinki.fi>
* Ilpo Järvinen | 2011-12-05 13:42:44 [+0200]:
>I disagree. If there's any slow starting flow that alone can fill the
>bottleneck, anything significantly larger than RTT just harms. RED is
>just "too slow" if you follow the recommended parametrization..
>
>In a core router you can probably get away with multiple RTTs, but near
>edge that is a grave mistake due to how slow-start behaves. With average
>based on many RTTs, RED still estimates that the link has low load while
>congestion has escalated to higher dimensions due to slow start. As a
>result, RED graciously falls back to tail-drop once the physical queue
>runs out and the flows respond allowing the load to decrease. However,
>finally RED reaches a state where it starts to "pro-actively" react to an
>"incipient congestion"?!? :-/ => Problem is made worse by those extra
>drops/marks happening too late.
But then one question Ilpo: drive IW10 or IW14 the behavior even worse?
Especially if n connections start almost simultanously? You did some analysis
on this topic.
HGN
next prev parent reply other threads:[~2011-12-07 22:57 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-30 20:25 [RFC iproute2] sch_red: TC_RED_HARDDROP Eric Dumazet
2011-11-30 22:36 ` Stephen Hemminger
2011-12-01 21:06 ` [PATCH] sch_red: fix red_change Eric Dumazet
2011-12-01 21:35 ` Dave Taht
2011-12-01 21:48 ` Jim Gettys
2011-12-01 21:57 ` Eric Dumazet
2011-12-01 22:04 ` Jim Gettys
2011-12-05 11:42 ` Ilpo Järvinen
2011-12-07 22:57 ` Hagen Paul Pfeifer [this message]
2011-12-02 0:25 ` David Miller
2011-11-30 23:29 ` [RFC iproute2] sch_red: TC_RED_HARDDROP Thomas Graf
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