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

From: Stephen Hemminger <[email-masked]>
Date: Tue, 12 Jun 2007 17:16:03 -0700

On Tue, 12 Jun 2007 15:12:58 -0700 (PDT)
David Miller <[email-masked]> wrote:

> From: Bill Fink <[email-masked]>
> Date: Wed, 16 May 2007 02:44:09 -0400
> 
> > [root@lang2 ~]# 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.