<%NUMBERING1%>.<%NUMBERING2%>.<%NUMBERING3%> 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 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)
  • MOS (Mean Opinion Score)
  • 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: QoS (Qualidade de serviço) Ida e volta, Russian: Цикл тестирования качества обслуживания, Simplified Chinese: QoS (服务质量) 往返, Spanish: QoS (Calidad de servicio) Round Trip

Remarks

icon-prtg-on-demandYou cannot add this sensor type to the Hosted Probe of a PRTG hosted by Paessler instance. If you want to use this sensor type, please 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 will not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

Sensor Settings

On the details page of a sensor, click the Settings tab to change its settings.

icon-i-roundUsually, a sensor connects to the IP Address or DNS Name of the parent device where you created this sensor. See the Device Settings for details. For some sensor types, you can define the monitoring target explicitly in the sensor settings. See below for details on available settings.

Basic Sensor Settings

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

Tags

Enter one or more Tags, separated by spaces or commas. You can use tags to group sensors and use tag–filtered views later on. Tags are not case sensitive. We recommend that you use the default value.

You can add additional tags to the sensor if you like. Other tags are automatically inherited from objects further up in the device tree. These are visible above as Parent Tags.

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

Priority

Select a priority for the sensor. This setting determines where the sensor is placed in sensor lists. Top priority is at the top of a list. Choose from one star (low priority) to five stars (top priority).

Quality of Service Measurement

Timeout (Sec.)

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

QoS Target

Define the type of target that will receive the UDP packets. Choose between:

  • PRTG Probe (recommended): The connection endpoint is a PRTG probe.
  • Custom Target: Choose this option if you want to use the PRTG QoS Reflector as connection endpoint.

icon-book-bulbFor more information about the QoS Reflector, see this Knowledge Base: How can I monitor QoS roundtrips without using remote probes?

Target Probe

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

When running the sensor on the PRTG on premises local probe, select a remote probe as 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 another remote probe or the local probe in PRTG on premises as target. The sensor will measure values for the network track between the probe the sensor is created on and the target probe.

icon-i-round-redYou must ensure that firewalls, NAT rules, etc. will allow the UDP packets to reach the target probe. The Windows firewall on the target system will be automatically opened by the probe. For details, see this Knowledge Base article: What connection settings are necessary for the QoS (Quality of Service) Round Trip Sensor?

icon-prtg-on-demandIn PRTG hosted by Paessler, you can only select another remote probe as target probe. QoS measurements for connections to the hosted probe are not 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 probe the sensor is created on connects.

icon-i-roundIf 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 will be 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.

icon-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. Please enter an integer value. Default value is 1000. We recommend that you use the default value.

Size of Packets (Bytes)

Define the size in bytes of the packets that the sensor sends. Please enter an integer value. 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. Please enter an integer value. Default value is 20. We recommend that you use the default value.

Sensor Display

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 will always be displayed below the sensor's name. The available options depend on what channels are available for this sensor.

icon-i-roundYou can set another primary channel later by clicking the pin symbol of a channel in the sensor's Overview tab.

Graph Type

Define how different channels will be shown for this sensor.

  • Show channels independently (default): Show an own 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 will generate an easy-to-read graph that visualizes the different components of your total traffic.
    icon-i-roundThis option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channel Settings settings).

Stack Unit

This setting is only available if stacked graphs are selected above. Choose a unit from the list. All channels with this unit will be 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 following settings are inherited from objects higher in the hierarchy and should be changed there, if necessary. Often, best practice is to change them centrally in the Root group's settings, see section Inheritance of Settings for more information. To change a setting only for this object, disable inheritance by clicking the button next to inherit from under the corresponding setting name. You will then see the options described below.

Scanning Interval

Click inherited_settings_button to disrupt the inheritance. See section Inheritance of Settings for more information.

Scanning Interval

Select a scanning interval (seconds, minutes, or hours) from the list. The scanning interval determines the time the sensor waits between two scans. You can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Define the number of scanning intervals that a sensor has time to reach and check a device again in case a sensor query fails. The sensor can try to re-reach and check a device several times, depending on the option you select here, before it will be set to a Down status. This helps you avoid false alarms if the monitored device has only temporary issues. For previous scanning intervals with failed requests, the sensor will show a Warning status. Choose between:

  • Set sensor to down immediately: The sensor will show an error immediately after the first failed request.
  • Set sensor to warning for 1 interval, then set to down (recommended): After the first failed request, the sensor will show a warning status. If the following request also fails, the sensor will show an error.
  • Set sensor to warning for 2 intervals, then set to down: Show an error status only after three consecutively failed requests.
  • Set sensor to warning for 3 intervals, then set to down: Show an error status only after four consecutively failed requests.
  • Set sensor to warning for 4 intervals, then set to down: Show an error status only after five consecutively failed requests.
  • Set sensor to warning for 5 intervals, then set to down: Show an error status only after six consecutively failed requests.

icon-i-roundSensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval until they show an error. It is not possible to set a WMI sensor to Down immediately, so the first option will not apply to these sensor types. All other options can apply.

icon-i-roundIf a sensor has defined error limits for channels, it will always show a Down status immediately, so no "wait" option will apply.

icon-i-roundIf a channel uses lookup values, it will always show a Down status immediately, so no "wait" options will apply.

Schedules, Dependencies, and Maintenance Window

icon-i-roundInheritance for schedules, dependencies, and maintenance windows cannot be interrupted. The corresponding settings from the parent objects will always be active. However, you can define additional settings here. They will be active at the same time as the parent objects' settings.

Schedule

Select a schedule from the list. Schedules can be used to monitor for a certain time span (days, hours) every week. With the period list option it is also possible to pause monitoring for a specific time span. You can create new schedules and edit existing ones in the account settings.

icon-i-roundSchedules are generally inherited. New schedules will be added to existing ones, so all schedules are active at the same time.

Maintenance Window

Specify if you want to set up a one-time maintenance window. During a "maintenance window" period, this object and all child objects will not be monitored. They will be in a Paused status instead. Choose between:

  • Not set (monitor continuously): No maintenance window will be set and monitoring will always be active.
  • Set up a one-time maintenance window: Pause monitoring within a maintenance window. You can define a time span for a monitoring pause below and change it even for a currently running maintenance window.

icon-i-roundTo terminate a current maintenance window before the defined end date, change the time entry in Maintenance Ends field to a date in the past.

Maintenance Begins

This field is only visible if you enabled the maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Maintenance Ends

This field is only visible if you enabled the maintenance window above. Use the date time picker to enter the end date and time of the maintenance window.

Dependency Type

Define a dependency type. Dependencies can be used to pause monitoring for an object depending on the status of another. You can choose between:

  • Use parent: Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency.
  • Select object: Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency. Additionally, pause the current sensor if a specific other object in the device tree is in Down status, or is paused by another dependency. Select below.
  • Master object for parent: Make this sensor the master object for its parent device. The sensor will influence the behavior of the device, where it is created on: If the sensor is in Down status, the device will be 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 will be paused if the parent group of its parent device is in Down status, or if it is paused by another dependency.

icon-i-roundTesting your dependencies is easy! Simply choose Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later all dependent objects should be paused. You can check all dependencies in your PRTG installation by selecting Devices | Dependencies from the main menu bar.

Dependency

This field is only visible if the Select object option is enabled above. Click on the reading-glasses and use the object selector to choose an object on which the current sensor will depend.

Dependency Delay (Sec.)

Define a time span in seconds for a dependency delay. After the master object for this dependency goes back to Up status, PRTG will start monitoring the depending objects after this extra delayed. This can help to avoid false alarms, for example, after a server restart, by giving systems more time for all services to start up. Please enter an integer value.

icon-i-round-redThis setting is not available if you choose this sensor to Use parent or to be the Master object for parent. In this case, please define delays in the parent Device Settings or in the superior Group Settings.

Access Rights

Click inherited_settings_button to disrupt the inheritance. See section Inheritance of Settings for more information.

User Group Access

Define which user group(s) will have access to the object you're editing. A table with user groups and types of access rights is shown. It contains all user groups from your setup. For each user group, you can choose from the following access rights:

  • Inherited: Use the access rights settings of the parent object.
  • None: Users in this group cannot see or edit the object. The object neither shows up in lists nor in the device tree. Exception: If a child object is visible to the user, the object is visible in the device tree, though not accessible.
  • Read: Users in this group can see the object and review its monitoring results.
  • Write: Users in this group can see the object, review its monitoring results, and edit the object's settings. They cannot edit access rights settings.
  • Full: Users in this group can see the object, review its monitoring results, edit the object's settings, and edit access rights settings.

You can create new user groups in the System Administration—User Groups settings. To automatically set all objects further down in the hierarchy to inherit this object's access rights, set a check mark for the Revert children's access rights to inherited option.

icon-book-arrowsFor more details on access rights, see section User Access Rights.

More

Knowledge Base: How does PRTG calculate the MOS score for QoS sensors?

Knowledge Base: How can I monitor QoS roundtrips without using remote probes?

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

Edit Sensor Channels

To change display settings, spike filter, and limits, switch to the sensor's Overview tab and click the gear icon of a specific channel. For detailed information, see the Sensor Channel Settings section.

Notifications

Click the Notification Triggers tab to change notification triggers. For detailed information, see the Sensor Notification Triggers Settings section.

Others

For more general information about settings, see the Object Settings section.

Sensor Settings Overview

For information about sensor settings, see the following sections:

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