netdev - Re: Linux TCP's Robustness to Multipath Packet Reordering

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Date:	Tue, 26 Apr 2011 18:58:58 +0200
From:	Dominik Kaspar <dokaspar.ietf@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Carsten Wolff <carsten@...ffcarsten.de>, netdev@...r.kernel.org
Subject: Re: Linux TCP's Robustness to Multipath Packet Reordering

Hi Eric,

On Mon, Apr 25, 2011 at 5:38 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> Since you have at sender a rule to spoof destination address of packets,
> you should make sure you dont send "super packets (up to 64Kbytes)",
> because it would stress the multipath more than you wanted to. This way,
> you send only normal packets (1500 MTU).
>
> ethtool -K eth0 tso off
> ethtool -K eth0 gso off
>
> I am pretty sure it should help your (atypic) workload.

I made new experiments with the exact same multipath setup as before,
but disabled TSO and GSO on all involved Ethernet interfaces. However,
this did not seem to change much about TCP's behavior when packets are
striped over heterogeneous paths. You can see the results of four
20-minute experiments on this plot:

http://home.simula.no/~kaspar/static/mptcp-emu-wlan-hspa-01-tos0.png

Cheers,
Dominik
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