Q. How are the "Time to establish connection" and "Round-trip time" values determined for the HTTP probe?

A. The "Time to establish connection" value is the value of the "${_connect}" macro. InterMapper starts this timer just before issuing the call to connect the socket, and, assuming there are no errors, stops it when the socket is polled (using the select call for the socket) and finds that it has connected.

The "Round-trip time" is the total of the connection time as described above and the time the probe is active after having connected. The _active timer is started at the same time that the _connect time is stopped, and runs until the socket is closed or the connection is otherwise broken.

Note that for a TCP probe requiring multiple connections, this information refers only to the last connection. The HTTP probe requires only one connection.