9e5cd3bf_mod_proxy___Apache_HTTP_Server__Description
[Parameter] keepalive [Default] Off [Description] 
This parameter should be used when you have a firewall between your Apache and the backend server, who tend to drop inactive connections. This flag will tell the Operating System to send KEEP_ALIVE messages on inactive connections and thus prevent the firewall to drop the connection. To enable keepalive set this property value to On. The frequency of initial and subsequent TCP keepalive probes depends on global OS settings, and may be as high as 2 hours. To be useful, the frequency configured in the OS must be smaller than the threshold used by the firewall.
mod_proxy - Apache HTTP Server
Description