[ovs-discuss] Simple test-setup: lots of TCP Retransmission, TCP Dup ACK

Jesse Gross jesse at nicira.com
Mon Jan 9 20:01:24 UTC 2012


On Sun, Jan 8, 2012 at 1:01 PM, Hans van Kranenburg
<hans.van.kranenburg at mendix.com> wrote:
> On 1/8/12 10:33 AM, Dave Whitla wrote:
>>
>>
>> The issue persists in all kernels on the 2.6 branch. I've not
>> experienced it with 3.x kernels but my scripts have disabled TX
>> checksumming since I first came across the issue.
>>
>> The problem is that many people run VMs to support "legacy" systems
>> on new high-capacity hardware or in production environments where we
>> are compelled to run say RHEL which doesn't ship with a kernel newer
>> than 2.6.35. So while this isn't an issue with OVS it probably should
>> be prominently mentioned somewhere in your doco if only to avoid it
>> appearing in list posts over and over.
>>
>> A fix belongs in Xen's netfront driver I think. I have assumed Hans
>> is using Xen.
>
>
> That's correct.
>
> I'm building a test setup for replacing numerous vlan-interfaces and bridges
> on a Xen setup using ovs on Debian GNU/Linux stable, which has linux 2.6.32
> and Xen 4.0.

In the setup that you've described, traffic isn't actually going
through any of Xen's network interfaces, right?  i.e. it's originating
on the OVS internal device rather than from a VM.

Assuming that's the case, I believe these two issues have different
root causes with different solutions.



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