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Subject: Re: svn commit: r242266 - head/sys/netinet
From: Rui Paulo <rpaulo@felyko.com>
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Date: Sun, 28 Oct 2012 14:44:21 -0700
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To: Andre Oppermann <andre@FreeBSD.org>
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On 28 Oct 2012, at 14:33, Andre Oppermann <andre@FreeBSD.org> wrote:
> IW10 has been heavily discussed on IETF TCPM.  A lot of research on
> the impact has been done and the overall result has been a significant
> improvement with very little downside.  Linux has adopted it for quite
> some time already as default setting.

I have followed the discussions at tcpm, but I did not find any =
conclusive evidence of the benefit of IW10. I'm sure it can help in =
multiple situations but, as always, there are tradeoffs. Section 6 of =
draft-ietf-tcpm-initcwnd never convinced me.

> The bufferbloat issue is certainly real and should not be neglected.
> However the solution to bufferbloat is not to send less packets into
> the network.  In fact that doesn't even make a difference simply =
because
> other packets with take their place.

Right, my point is that sending more packets in an already congested =
link will negatively affect the throughput / latency of the network. I'm =
not saying that it won't help you download a YouTube video faster, but =
the overall fairness of TCP will be reduced.

>  Buffer bloat can only be fixed
> in the devices that actually do the buffering.  A much discussed and
> apparently good approach seems to be the Codel algorithm for active
> buffer management.


Are you working on CoDel? :-)

Regards,
--
Rui Paulo