netdev - Re: Raise initial congestion window size / speedup slow start?

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Message-ID: <20100714221301.GI6682@nuttenaction>
Date:	Thu, 15 Jul 2010 00:13:01 +0200
From:	Hagen Paul Pfeifer <hagen@...u.net>
To:	David Miller <davem@...emloft.net>
Cc:	rick.jones2@...com, lists@...dgooses.com, davidsen@....com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: Raise initial congestion window size / speedup slow start?

* David Miller | 2010-07-14 14:55:47 [-0700]:

>Although section 3 of RFC 5681 is a great text, it does not say at all
>that increasing the initial CWND would lead to fairness issues.

Because it is only one side of the medal, probing conservative the available
link capacity in conjunction with n simultaneous probing TCP/SCTP/DCCP
instances is another.

>To be honest, I think google's proposal holds a lot of weight.  If
>over time link sizes and speeds are increasing (they are) then nudging
>the initial CWND every so often is a legitimate proposal.  Were
>someone to claim that utilization is lower than it could be because of
>the currenttly specified initial CWND, I would have no problem
>believing them.
>
>And I'm happy to make Linux use an increased value once it has
>traction in the standardization community.

Currently I know no working link capacity probing approach, without active
network feedback, to conservatively probing the available link capacity with a
high CWND. I am curious about any future trends.

>But for all we know this side discussion about initial CWND settings
>could have nothing to do with the issue being reported at the start of
>this thread. :-)

;-) sure, but it is often wise to thwart these kind of discussions. It seems
these CWND discussions turn up once every other month. ;-)

Hagen

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