[Beowulf] tg3 driver and rx dropped packets

Greg Lindahl lindahl at pbm.com
Fri Dec 18 11:36:35 PST 2009

On Fri, Dec 18, 2009 at 08:40:47AM -0500, Michael Di Domenico wrote:

> I hooked up wireshark on one of the servers while we were running the
> test and i see a lot of Duplicate ACK and TCP Checksum errors, in the
> communications between the two hosts.  But im not sure that actually
> points to anything.

Well, it points to there being a significant problem. Packets are
protected on the wire by a strong checksum, and so if there's
corruption, it should be detected there. If that checksum is correct
but the weak TCP checksum is wrong, that means something corrupted the
packet in the host, for example a bad PCI card.

The TCP checksum is so weak that if you see a lot of errors detected,
you probably have some undetected errors sneaking through.

-- greg

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