Large number of "invalid SYN cookies" on RHEL 7 running httpd

Issue

• netstat shows a large number of "invalid SYN cookies"
• httpd terminates sessions earlier than expected, causing clients to reconnect and increasing latency.
• When comparing http traffic between RHEL 6 and RHEL 7, this issue may appear as a lower than expected number of connections and httpd workers on RHEL 7.