From: Mika Liljeberg <Mika.Liljeberg@welho.com>
To: "David S. Miller" <davem@redhat.com>
Cc: cwidmer@iiic.ethz.ch, linux-kernel@vger.kernel.org
Subject: Re: unnecessary retransmit from network stack
Date: Sat, 06 Oct 2001 12:59:52 +0300 [thread overview]
Message-ID: <3BBED618.768332@welho.com> (raw)
In-Reply-To: <200110051229.f95CTvN00624@mail.swissonline.ch> <20011005.161105.78709492.davem@redhat.com>
"David S. Miller" wrote:
>
> From: Christian Widmer <cwidmer@iiic.ethz.ch>
> Date: Fri, 5 Oct 2001 14:29:53 +0200
>
> why does net_dev.hard_start_xmit get called multiple times
> with the same tcp packet?
>
> Because the ACK is not coming back for those packets within the RTO
> (which for a local network is very low). Check your TCP dumps,
> the ACKs of the original data packets are being dropped in transit.
Well, TCP certainly shouldn't be sending two retransmissions
back-to-back within 2ms, especially with nothing received in between.
Not with RTO (which in Linux is never below 20ms, and according to RFC
should be conservatively rounded up to 1 second), nor with fast
retransmits or SACK.
Just an observation.
MikaL
next prev parent reply other threads:[~2001-10-06 10:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-10-05 12:29 unnecessary retransmit from network stack Christian Widmer
2001-10-05 23:11 ` David S. Miller
2001-10-06 9:59 ` Mika Liljeberg [this message]
-- strict thread matches above, loose matches on Subject: below --
2001-10-06 11:18 Manfred Spraul
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