As Wikipedia explains:
HTTP persistent connection, also called HTTP keep-alive, or HTTP connection reuse, is the idea of using a single TCP connection to send and receive multiple HTTP requests/responses, as opposed to opening a new connection for every single request/response pair. The newer SPDY protocol uses the same idea and takes it further to allow multiple concurrent requests/responses to be multiplexed over a single connection.
Note: I assume you have adequate knowledge of handling your server & server settings & you are well versed in your field
You can put following code in your .htaceess file which is available in your root of your server’s html folder
<ifModule mod_headers.c> Header set Connection keep-alive </ifModule>
After completing above procedure you are good to go,
But know you may be wondering above settings are working or not i.e. Keep Alive settings are on or not on your domain
Now go to & open Terminal App available on OSX in Applications > Utilities folder
curl -Iv http://your-domain-name.com 2>&1 | grep -i 'connection #0'
Note: put your domain name in url of above code
Then after executing above code in Terminal, If you get result something like this:
* Connection #0 to host your-domain-name.com left intact
Understand that Keep Alive is working on your server for your domain.
Hope it helps,
Thanks & Regards