Oops, I meant to mention this too .... virtually all GigE and/or server class NICs do TCP checksum offload.
Dimitri - it's unlikely that you have a hardware issue on the NIC, it's more likely to be a cable problem or network congestion. What you want to look for in the tcpdump capture is things like SYN retries. A good way to test for cable issues is to use a ping flood with a large packet size. Cheers Dave Hang on a sec. You need to ignore bad checksums on *outbound* packets, > because many (most?) Ethernet drivers implement some level of TCP > offloading, and this will result in packet sniffers seeing invalid checksums > for transmitted packets - the checksums haven't been generated by the NIC > yet. > > Unless you know for sure that your NIC doesn't do TSO, ignore bad checksums > on outbound packets from the local interface. > > -- > Craig Ringer > > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance >
