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Understanding response time




The HTTP Advanced sensor can show split up times for first byte, loading time etc. However IMAP sensor, POP3 sensor, Port sensor and alike show only response time. I need to know what exactly is the response time. Is it only the time for the connection to the specific port say to the IMAP server port, or it is the time of connection plus the time of the first byte received or perhaps the time till the server ready-hello message is fully received?


imap port response

Created on Mar 24, 2013 2:09:49 AM

3 Replies

Accepted Answer



Dear mfrenk,

unfortunately, there is no general answer to this, as we have more than 150 sensor types which all monitor different aspects of your network. Usually, i.e., for most sensor types, the response time measures the time necessary for the sensor to complete the monitoring job.

In case of the port sensor, this includes: opening a connection, retrieving values from a remote server, and processing them according to filters or conditions (e.g. must include, etc.). The response time does not include the time necessary for DNS resolution of the hostname.

In case of the Ping sensor, the response time gives back the time necessary for the ICMP echo request to be sent back to the PRTG core server (also without DNS resolution)—which will be similar to the times measured when using the "ping" command in a console on the machine running the PRTG probe.

An exception applies to the HTTP Advanced sensor which splits up response times explicitly for most exact return values.

Created on Mar 26, 2013 2:21:15 PM by  Daniel Zobel [Product Manager]



Thank you very much for the response.

I would be grateful if you explain me about POP3 monitoring specifically. As I understood, if I only want to monitor the time it takes to connect to a POP3 server I should be using custom Port Sensor without content filters. That configuration will return only the time to establish TCP connection to a specific IP and port and not the time to receive the first welcome message from the POP3 service.

However, if I want to monitor the time that includes the following:

  1. Port connection time
  2. Time to handle SSL
  3. Time to receive POP3 service welcome message I should be using the POP3 sensor instead.

Am I correct?


Created on Mar 26, 2013 2:43:10 PM

Last change on Apr 2, 2013 7:52:54 AM by  Daniel Zobel [Product Manager]



I reassured with our developers:

The POP3 sensor connects to the server (optionally establishes an SSL connection, if activated), then it does the following: "Connect sets the value in GreetingBanner using the POP3 response from the server, and calls CAPA to determine if Capabilities are supported on the server implementation."

PRTG measures the time necessary to complete the entire process.

And yes, to only monitor the time it takes to establish a TCP connection to a port, please use a port sensor without additional options.

Created on Apr 3, 2013 12:39:44 PM by  Daniel Zobel [Product Manager]

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