Wireshark-users: Re: [Wireshark-users] Wondering about TCP checksum errors in AFP-over-TCP
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?
More info on this: I'm beginning to think that the LACP/IEEE802.3ad
bonding of the server with the switch has nothing to do with it as I'm
seeing the same checksum errors between the client (which only has one
NIC and doesn't use LACP/IEEE802.3ad) and public servers hosted at
akamai.net, doubleclick.com, etc., and even my externally hosted mail
server.
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