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Wireshark-users: Re: [Wireshark-users] Large Packages although TSO is off

From: Martin Visser <martinvisser99@xxxxxxxxx>
Date: Mon, 27 Sep 2010 12:31:04 +1000
The only thing I am wondering is whether you have turned off "tcp segmentation offload" at the physical level of the server, but it is still on at the virtual machine guest level. (You haven't said you are running in virtualised environment, but I had this issue).

Do you think this is causing a network operation issue, or is just that wireshark isn't showing the data you expect?

Regards, Martin

MartinVisser99@xxxxxxxxx


On Fri, Sep 24, 2010 at 11:35 PM, Estanislao Gonzalez <estanislao.gonzalez@xxxxxxx> wrote:
 Hi,

I've been reading a lot lately, but I still can't find the source of my
problem.

For example this is a captured package at eth0:

6249    10.090368       remote.ip       local.ip        TCP     51402>  50383 [ACK] Seq=56628006 Ack=1578 Win=9216 Len=18824 TSV=240912663 TSER=21362093

These are the current settings:
# ethtool -k eth0
Offload parameters for eth0:
Cannot get device udp large send offload settings: Operation not supported
rx-checksumming: on
tx-checksumming: on
scatter-gather: off
tcp segmentation offload: off
udp fragmentation offload: off
generic segmentation offload: off
generic-receive-offload: off

(I've already tried turning checksumming also off)

The TCP options are set to avoid reassembling streams and not to
validate checksums.

If MTU is set to 9000 for the receiver, and 1500 for the sender, why am
I still seeing large packages?

Any idea?

Thanks,
Estani

--
Estanislao Gonzalez

Max-Planck-Institut für Meteorologie (MPI-M)
Deutsches Klimarechenzentrum (DKRZ) - German Climate Computing Centre
Room 108 - Bundesstrasse 45a, D-20146 Hamburg, Germany

Phone:   +49 (40) 46 00 94-126
E-Mail:  estanislao.gonzalez@xxxxxxx

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