The TCP_INFO option provides information about round trip times ( RTT ) for a TCP connection. Turns out that Nginx can expose this information for you as embedded variables:
$tcpinfo_rtt, $tcpinfo_rttvar, $tcpinfo_snd_cwnd, $tcpinfo_rcv_space
information about the client TCP connection; available on systems that support the TCP_INFO socket option
Easy to log this information. From there: periodically parse Nginx logs looking for client IP and RTT data, GEO IP lookup on the client, compute the median RTT value for each country/state, color code countries from highest to lowest RTT, then use Google Maps for the display.
You’ll have yourself a nice page showing the RTT values across the world for visitors to your site.