Measuring TCP Response Times
You can measure the response time, in milliseconds, of a device as it is tested by a TCP probe.
With TCP Probes, Intermapper measures both the time to establish the connection and the time for various portions of an interaction. These times can be charted and logged.
Time Measurement Probe Variables
| Connection initiation interval | ${_connect} | Records the time required to establish a connection. |
| Connection duration interval | ${_active} | Records the duration from the connection request until the end of the end of the script. |
TCP Script Commands
Intermapper supports the following commands for measuring intervals during a script:
| STRT | Starts the probe's custom timer. |
| TIME varname | Sets the variable named ${varname} to the milliseconds elapsed since the customtimer started. |
The <script-output> Section
Use the optional <script-output> section to display the results of custom TCP probes. The data in this section is displayed in the Status window when you click and hold the device. The format of this section is the same as the <snmp-device-display>, described in Customized Status Windows.
Use the ${_connect} and ${_active} variables, as well as any variables set with the TIME varname command, in the <script-output> section of the Status window.
Accuracy
Intermapper uses the following techniques to measure the round-trip times of various probes:
- Pings (ICMP and AppleTalk echoes) - These are the most accurate timings. Intermapper detects the arrival of the Ping response as soon as it arrives. Therefore, it can compute the response times with millisecond accuracy.
- Other UDP-based and TCP-based probes - These timings are computed by Intermapper as it does its normal polling. Therefore, the measured time can be affected slightly by the such things as the number of devices probed and other various other tasks, as they can affect how long it takes Intermapper to execute a single round of polling.