Test Agents: Frequently asked questions¶
What is the measurement accuracy of Test Agents?¶
Thanks to the Test Agent being an appliance, the accuracy of its measurements is very good. A Test Agent has full control of the underlying hardware on which you install it, and the appliance makes sure that no unknown or unnecessary processes are consuming CPU cycles. This results in the highest possible precision in all measurements. The Paragon Active Assurance implementation also ensures that network packet processing always gets top priority in the CPU.
What is the data rate of the control traffic from a Test Agent to the Paragon Active Assurance server?¶
The bandwidth of the control traffic to and from the server is typically just a few kbit/s during execution of tests or monitoring sessions. When a Test Agent is in idle mode, there is virtually no traffic towards the Paragon Active Assurance server.
What happens if the management link between a Test Agent and the Paragon Active Assurance server is lost?¶
All your Test Agents will continue their activities even if the connection to the Paragon Active Assurance server is temporarily lost. The Test Agent will store all measurements locally for up to one hour and upload them to the Paragon Active Assurance server at a later time when the connection is restored. If the connection stays down for more than one hour, all measurements from the time when the connection dropped and onward will be lost.
If you are running a distributed and automated test, it will be prematurely stopped if one of the Test Agents becomes unavailable during the test.
What is meant by the message “Time offset is too high” received when I try to start a test or monitoring session?¶
Test Agents synchronize their internal clocks using NTP (Network Timing Protocol). This is needed for one-way delay measurements.
The sender Test Agent adds a timestamp in the packet, and the receiver Test Agent compares this timestamp to its own time. Thanks to the clocks in the two Test Agent being synchronized, it is possible to calculate the delay.
However, if a Test Agent has for example just been connected and powered on, it may take a few minutes until the clock has acquired the requisite accuracy. In this case, therefore, Paragon Active Assurance issues a warning rather than allowing the test or monitoring session to start with insufficient accuracy.
This is particularly important for real-time services where delay is important, such as VoIP and videoconferencing. For UDP and SIP, the maximum allowed deviation of the Test Agent’s internal clock is 4 ms.
TCP-based services have less stringent timing requirements, so the maximum clock deviation in Paragon Active Assurance is set to 100 ms in this case.
Do Test Agents require calibration?¶
No calibration is needed for Test Agents. Calibration is most relevant for hardware-based components with extremely high accuracy (in the order of nanoseconds).
If I use a USB-based Test Agent on my laptop, will it affect my previous installation?¶
No. For a USB-based Test Agent, all required software is embedded in the USB flash memory, including the operating system as well as all required test tools.
The USB-based Test Agent uses your laptop hardware only temporarily. The laptop boots based on the contents on the USB, and as long as the laptop remains turned on, your laptop will act as a Test Agent.
Once you remove the USB and restart the laptop using a normal hard disk boot, your laptop will revert to its normal state.
Is the USB-based Test Agent dependent on the previous OS on the PC/laptop?¶
No, it does not matter what operating system you have on your computer prior to using it as a USB-based Test Agent.
When you download and create your bootable USB memory, a custom OS is also included. The computer then boots this OS using your downloaded USB contents. You might even use a USB Test Agent on a PC that does not have a hard disk installed.
Is it possible to install a downloadable Test Agent on Apple hardware?¶
No, this is currently not supported.