Got it. Thanks. I found the preference for "Validate TCP checksums if possible" and deselected it. I guess this leaves me kind of "flying blind" if there are legitimate TCP checksum errors as I was hoping the "if possible" in the above preference would somehow take into account TCP offloading but I suppose it can't. Oh well...
On Sun, Mar 27, 2011, at 12:52, Anders Broman wrote: Kok-Yong Tan skrev 2011-03-27 16:51: It says that "Wireshark 1.2 and above disable IP, TCP and UDP checksum by default." Does this mean that it disables checksum [validation] by default? If so, note that I'm running Wireshark 1.4.3 with default settings on a MacOS X 10.5.8 system and I'm still seeing the TCP checksum errors.
If you upgraded from an earlier version your (old)preferences will be retained... /Anders On Sun, Mar 27, 2011, at 01:19, Martin Visser wrote: In pretty much all case where you are seeing TCP checksum errors on a server, it will because of the various TCP offload features of the NIC / driver. If can capture on the wire (that is using port-mirroring on a switch) this will confirm this, or alternatively turn off those features on your server temporarily while testing.
Regards, Martin MartinVisser99@xxxxxxxxx On 27 March 2011 10:07, Kok-Yong Tan <ktan@xxxxxxxxxxxxxxxxxxx> wrote: On Sat, Mar 26, 2011, at 18:53, Kok-Yong Tan wrote: Just for kicks, I decided to do a wireshark trace of AFP-over-TCP conversations between my Apple MacOS X 10.4.11 Tiger server and my Apple MacOS X 10.5.8 Leopard (PPC) client. Surprisingly, I'm seeing lots of TCP checksum errors (no ssh going on here in the connection since it's all protected on my internal LAN) on packets going in both directions. Now, if the TCP stack were damaged either on the client or the server or both, I would expect connection issues and all packets going through to exhibit the checksum errors. But I don't and not all packets are exhibiting checksum errors between the two machines. Only some. Of course, this is manifesting itself in slower than expected throughput between the server and client since I assume that TCP checksum errors result in retransmits. The server is connected to a ZyXEL GS2024 switch via LACP 802.3ad with 1 IP address in use in the two-NIC bonded pipe. Could this be causing the TCP checksum errors?
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