SYNs to LISTEN sockets ignored rising

Hi,

I am testing the performance of a proxy and when I try to open many
connections per second, I see the "SYNs to LISTEN sockets ignored"
counter in the output of "netstat -s -t" rising.

Can anybody tell me what could be the reason for this increase?

From the text, I have assumed that the counter reflects the number of
SYNs received by the proxy that have not been processed by it. But
somebody has told me that it could also show the number of SYNs that
the proxy has sent to the final webserver and that have not been
answered.

In either case, what could be the reason for these SYNs not being
processed? None of the machines (proxy and final server) have shown a
CPU utilization of more than 50-60%, no swapping, nothing...

BTW, another parameter that grows significantly is the "times the
listen queue of a socket overflowed". What does this mean?

Regards,
Fran