ICMP echo is a standard technique for testing round-trip times for a packet of data sent from your PC to a remote server which sends it back. It's typically referred to as a 'ping' after the name of the utility usually used to do it.
This is an HTTP alternative: My Spider will respond with a 'Redirect', telling your browser to load this page again. The server will record the times between your browser's requests and present them to you after the number of redirects you select. Try it!