PRTG Manual: QoS (Quality of Service) Round Trip Sensor

The QoS (Quality of Service) Round Trip sensor monitors parameters regarding the quality of a network connection between two probes. This is important, for example, when using Voice over IP (VoIP) over this connection.

The sensor sends a series of User Datagram Protocol (UDP) packets from the source probe to a target at the end of the connection line. Then, the packets are sent back to the original probe ("round trip").

The sensor measures the following parameters:

  • Jitter in milliseconds (maximum, minimum, average)
  • Packet delay variation in milliseconds (maximum, minimum, average)
  • Mean opinion score (MOS)
  • Corrupted packets in percent
  • Duplicated packets in percent
  • Lost packets in percent
  • Packets out of order in percent
  • Round-trip time (RTT) in milliseconds (maximum, minimum, average)
  • Time to last packet in milliseconds
QoS (Quality of Service) Round Trip Sensor

QoS (Quality of Service) Round Trip Sensor

Sensor in Other Languages

  • Dutch: QoS (Quality of Service) Heen en weer
  • French: Aller-retour du QoS (Quality of Service)
  • German: QoS (Quality of Service) Round Trip
  • Japanese: ラウンドトリップ QoS(Quality of Service)
  • Portuguese: Percurso de ida e volta QoS (Qualidade de serviço)
  • Russian: Цикл тестирования качества обслуживания
  • Simplified Chinese: QoS (服务质量) 往返
  • Spanish: Ida y vuelta QoS (Calidad de servicio)

Remarks

  • You have to configure at least one remote probe in your PRTG on premises setup and at least two remote probes in PRTG hosted by Paessler, or you need to set up the PRTG QoS Reflector tool on the target machine at the endpoint of the monitored connection.
  • This sensor has a high performance impact.

i_podYou cannot add this sensor to the hosted probe of a PRTG hosted by Paessler instance. If you want to use this sensor, add it to a remote probe device.

Add Sensor

The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the setting fields that are required for creating the sensor. Therefore, you do not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

Basic Sensor Settings

Click the Settings tab of a sensor to change its settings.

i_round_blueUsually, a sensor connects to the IP Address or DNS Name of the parent device on which you created the sensor. See the device settings for details. For some sensors, you can explicitly define the monitoring target in the sensor settings. See below for details on available settings.

Setting

Description

Sensor Name

Enter a meaningful name to identify the sensor. By default, PRTG shows this name in the device tree, as well as in alarms, logs, notifications, reports, maps, libraries, and tickets.

Parent Tags

Shows tags that the sensor inherits from its parent device, parent group, and parent probe. This setting is shown for your information only and cannot be changed here.

Tags

Enter one or more tags. Confirm each tag with the Spacebar key, a comma, or the Enter key. You can use tags to group objects and use tag-filtered views later on. Tags are not case-sensitive. Tags are automatically inherited.

i_round_blueIt is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).

The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:

  • qossensor

Priority

Select a priority for the sensor. This setting determines the position of the sensor in lists. The highest priority is at the top of a list. Choose from the lowest priority (i_priority_1) to the highest priority (i_priority_5).

Quality of Service Measurement

Setting

Description

Timeout (Sec.)

Enter a timeout in seconds for the request. If the reply takes longer than this value, the sensor cancels the request and shows a corresponding error message. Enter an integer value. The maximum value is 900 seconds (15 minutes).

QoS Target

Define the type of target that receives the UDP packets:

  • PRTG probe (recommended): The connection endpoint is a probe.
  • Custom target: Use the PRTG QoS Reflector as connection endpoint.

i_square_cyanFor more information about the QoS Reflector, see the Knowledge Base: How can I monitor QoS round trips without using remote probes?

Target Probe

This setting is only available if you select PRTG probe as QoS target. In the dropdown list, you see all local probes and remote probes of your setup.

When running the sensor on the local probe, select a remote probe as the Target Probe. If no remote probe is available, install and connect a remote probe first or use the PRTG QoS Reflector.

When running the sensor on a remote probe, select either a different remote probe or the local probe in PRTG on premises as target. The sensor measures values for the network track between the parent probe and the target probe.

i_round_redYou must ensure that firewalls or network address translation (NAT) rules allow the UDP packets to reach the target probe. The Windows firewall on the target system is automatically opened by the probe. For details, see the Knowledge Base: What connection settings are necessary for the QoS (Quality of Service) Round Trip Sensor?

i_podIn PRTG hosted by Paessler, you can only select a different remote probe as the target probe. QoS measurements for connections to the hosted probe are not possible.

Target Host/IP

Define the IP address of the QoS target. If you use the QoS Reflector, enter the address of the machine on which the reflector script runs. If you use a probe, enter the address of the probe to which the parent probe connects.

i_round_blueIf you do not use NAT rules, this is usually the address shown above (next to the target probe's name).

Port

Define the source and target port for the UDP packets. This port is used on both the source and target probe. Use a different port for each QoS sensor to make sure packets can be assigned correctly. Enter an integer value between 1024 and 65536.

i_round_redThis port must be available on both the source and target system.

Number of Packets

Define how many packets the sensor sends for each scanning interval. Enter an integer value. The default value is 1000. We recommend that you use the default value.

Size of Packets (Bytes)

Define the size of the packets in bytes that the sensor sends. Enter an integer value. The default value is 172. We recommend that you use the default value.

Time between Packets (ms)

Define the time in milliseconds that the sensor waits between two packets. Enter an integer value. The default value is 20. We recommend that you use the default value.

Sensor Display

Setting

Description

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel is always displayed below the sensor's name. The available options depend on what channels are available for this sensor.

i_round_blueYou can set a different primary channel later by clicking b_channel_primary below a channel gauge on the sensor's Overview tab.

Graph Type

Define how different channels are shown for this sensor:

  • Show channels independently (default): Show a graph for each channel.
  • Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This generates a graph that visualizes the different components of your total traffic.
    i_round_redYou cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).

Stack Unit

This setting is only visible if you enable Stack channels on top of each other as Graph Type. Select a unit from the list. All channels with this unit are stacked on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Inherited Settings

By default, all of the following settings are inherited from objects that are higher in the hierarchy. You should change them centrally in the root group settings if necessary. To change a setting for this object only, click b_inherited_enabled under the corresponding setting name to disable the inheritance. You then see the options described below.

i_square_cyanFor more information, see section Inheritance of Settings.

Scanning Interval

Click b_inherited_enabled to interrupt the inheritance.

Setting

Description

Scanning Interval

Select a scanning interval from the dropdown list. The scanning interval determines the amount of time that the sensor waits between two scans. Choose from:

  • 30 seconds
  • 60 seconds
  • 5 minutes
  • 10 minutes
  • 15 minutes
  • 30 minutes
  • 1 hour
  • 4 hours
  • 6 hours
  • 12 hours
  • 1 day

i_round_blueYou can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Select the number of scanning intervals that the sensor has time to reach and to check a device again if a sensor query fails. Depending on the option that you select, the sensor can try to reach and to check a device again several times before the sensor shows the Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor shows the Warning status. Choose from:

  • Set sensor to down immediately: Set the sensor to the Down status immediately after the first request fails.
  • Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to the Warning status after the first request fails. If the second request also fails, the sensor shows the Down status.
  • Set sensor to warning for 2 intervals, then set to down: Set the sensor to the Down status only after the third request fails.
  • Set sensor to warning for 3 intervals, then set to down: Set the sensor to the Down status only after the fourth request fails.
  • Set sensor to warning for 4 intervals, then set to down: Set the sensor to the Down status only after the fifth request fails.
  • Set sensor to warning for 5 intervals, then set to down: Set the sensor to the Down status only after the sixth request fails.

i_round_blueSensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval before they show the Down status. It is not possible to immediately set a WMI sensor to the Down status, so the first option does not apply to these sensors. All other options can apply.

i_round_blueIf you define error limits for a sensor's channels, the sensor immediately shows the Down status. None of the interval options apply.

i_round_blueIf a channel uses lookup values, the sensor immediately shows the Down status. None of the interval options apply.

Schedules, Dependencies, and Maintenance Window

i_round_blueYou cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. The corresponding settings from the parent objects are always active. However, you can define additional schedules, dependencies, and maintenance windows. They are active at the same time as the parent objects' settings.

Setting

Description

Schedule

Select a schedule from the list. You can use schedules to monitor during a certain time span (days or hours) every week. Choose from:

  • None
  • Saturdays
  • Sundays
  • Weekdays
  • Weekdays Eight-To-Eight (08:00 - 20:00)
  • Weekdays Nights (17:00 - 09:00)
  • Weekdays Nights (20:00 - 08:00)
  • Weekdays Nine-To-Five (09:00 - 17:00)
  • Weekends

i_square_cyanYou can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Schedules.

Maintenance Window

Select if you want to set up a one-time maintenance window. During a maintenance window, monitoring stops for the selected object and all child objects. They show the Paused status instead. Choose between:

  • Not set (monitor continuously): Do not set up a one-time maintenance window. Monitoring is always active.
  • Set up a one-time maintenance window: Set up a one-time maintenance window and pause monitoring. You can define a time span for a the pause below.

i_round_blueTo terminate an active maintenance window before the defined end date, change the time entry in Maintenance Ends to a date in the past.

Maintenance Begins

This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the one-time maintenance window.

Maintenance Ends

This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the end date and time of the one-time maintenance window.

Dependency Type

Select a dependency type. You can use dependencies to pause monitoring for an object depending on the status of a different object. You can choose from:

  • Use parent: Use the dependency type of the parent object.
  • Select a sensor: Use the dependency type of the parent object. Additionally, pause the current object if a specific sensor is in the Down status or in the Paused status because of another dependency.
  • Master sensor for parent: Make this sensor the master object for its parent device. The sensor influences the behavior of its parent device: If the sensor is in the Down status, the device is paused. For example, it is a good idea to make a Ping sensor the master object for its parent device to pause monitoring for all other sensors on the device in case the device cannot even be pinged. Additionally, the sensor is paused if the parent group is paused by another dependency.

i_round_blueTo test your dependencies, select Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later, all dependent objects are paused. You can check all dependencies under Devices | Dependencies in the main menu bar.

Dependency

This setting is only visible if you enable Select a sensor above. Click b_search_light and use the object selector to select a sensor on which the current object will depend.

Dependency Delay (Sec.)

This setting is only visible if you enable Select a sensor above. Define a time span in seconds for the dependency delay.

After the master sensor for this dependency returns to the Up status, PRTG additionally delays the monitoring of the dependent objects by the time span you define. This can prevent false alarms, for example, after a server restart or to give systems more time for all services to start. Enter an integer value.

i_round_redThis setting is not available if you set this sensor to Use parent or to be the Master sensor for parent. In this case, define delays in the parent device settings or in its parent group settings.

Access Rights

Click b_inherited_enabled to interrupt the inheritance.

Setting

Description

User Group Access

Define the user groups that have access to the sensor. You see a table with user groups and group access rights. The table contains all user groups in your setup. For each user group, you can choose from the following group access rights:

  • Inherited: Inherit the access rights settings of the parent object.
  • No access: Users in this user group cannot see or edit the sensor. The sensor neither shows up in lists nor in the device tree.
  • Read access: Users in this group can see the sensor and view its monitoring results. They cannot edit any settings.
  • Write access: Users in this group can see the sensor, view its monitoring results, and edit its settings. They cannot edit its access rights settings.
  • Full access: Users in this group can see the sensor, view its monitoring results, edit its settings, and edit its access rights settings.

i_square_cyanFor more details on access rights, see section Access Rights Management.

More

i_square_blueKNOWLEDGE BASE

How does PRTG calculate the MOS score for QoS sensors?

How can I monitor QoS round trips without using remote probes?

What connection settings are necessary for the QoS (Quality of Service) Round Trip Sensor?

 

i_square_bluePAESSLER WEBSITE

How to connect PRTG through a firewall in 4 steps

Sensor Settings Overview

For more information about sensor settings, see the following sections: