netdev - Re: 2.6.20.7 TCP cubic (and bic) initial slow start way too slow?

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Date:	Tue, 12 Jun 2007 17:16:03 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	David Miller <davem@...emloft.net>
Cc:	billfink@...dspring.com, sangtae.ha@...il.com, rhee@....ncsu.edu,
	rhee@...u.edu, netdev@...r.kernel.org
Subject: Re: 2.6.20.7 TCP cubic (and bic) initial slow start way too slow?

On Tue, 12 Jun 2007 15:12:58 -0700 (PDT)
David Miller <davem@...emloft.net> wrote:

> From: Bill Fink <billfink@...dspring.com>
> Date: Wed, 16 May 2007 02:44:09 -0400
> 
> > [root@...g2 ~]# netstat -s | grep -i retrans
> >     25446 segments retransmited
> >     20936 fast retransmits
> >     4503 retransmits in slow start
> >     4 sack retransmits failed
> > 
> > It then only took 2.14 seconds to transfer 1 GB of data.
> > 
> > That's all for now.
> 
> Thanks for all of your testing and numbers Bill.
> 
> Inhong et al., we have to do something about this, the issue
> has been known and sitting around for weeks if not months.
> 
> How safely can we set the default initial_ssthresh to zero in
> Cubic and BIC?

Yes. set it to zero. The module parameter could even go, and just
leave the route metric as a way to set/remember it.
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