7.8 Setting Assessment Options

Now that you have learned how to design, schedule, verify, and run a VoIP Quality assessment, you are ready to try out some of the extra features of Vivinet Assessor. If you have Performance Endpoints installed, Vivinet Assessor offers extensive options for customizing your VoIP implementation. You can also try out different VoIP optimizations, such as QoS, silence suppression, and jitter buffer sizes.

Assessment Options let you control how data is shown in VoIP Readiness reports, how the VoIP Quality assessment runs through a firewall on the network, and whether the Scheduler service should stop the assessment if the returned results are poor enough.

To set assessment options:

  1. In the Assess VoIP Quality view, click Assessment Options on the Options menu.

  2. Set the report parameters that determine quality standards for voice over IP on your network. For more information, see Section 7.8.1, Setting Result Ranges.

  3. Set the Vivinet Assessor reporting port, the port used when the endpoints report results back to the Console. For more information, see Section 7.8.2, Working with Firewalls.

  4. Determine whether, and how quickly, the Scheduler should stop a running assessment if preliminary results are extremely poor. For more information, see Section 7.8.3, Configuring Stop-Assessment Thresholds.

  5. Set thresholds that determine when additional diagnostic information will be automatically gathered for a call group. For more information, see Section 7.9.3, Configuring the Vivinet Diagnostics Integration.

  6. Control how measurements are taken and reported during the VoIP Quality assessment. For more information, see Section 7.8.4, Setting Assessment Run Options.

  7. To revert changed fields to their default values, click Restore Defaults.

  8. Click OK.

7.8.1 Setting Result Ranges

You can control how Vivinet Assessor evaluates the quality of VoIP calls on your network.

To set reporting result ranges:

  1. From the Assess VoIP Quality view, click Assessment Options on the Options menu, and then click the Result Ranges tab.

  2. Set one or all of the ranges for the different reporting parameters:

    Parameter

    Description

    Call Quality

    Determines how MOS estimates are mapped to VoIP quality ratings. The MOS scale runs from 1 to 5, with 1 representing the lowest quality. Vivinet Assessor rates call quality as Poor, Acceptable, or Good. Enter numbers from 1 to 5, inclusive, to determine which Mean Opinion Scores are rated Good and Acceptable; all lower scores are then rated Poor. For more information, see Section 8.5.1, Mean Opinion Score.

    Delay

    Determines how delay (latency) is mapped to VoIP quality ratings. Set the maximum amount of delay (in milliseconds) that a call can have if its quality is rated Good or Acceptable. Any call with higher delay is then rated Poor. For more information, see Section 8.5.2, Delay.

    Lost data

    Determines how data loss is mapped to VoIP quality ratings. Set the maximum amount of datagrams lost (in % of total datagrams sent) that a call can have if its quality is rated Good or Acceptable. Any call with a higher percentage of data loss is then rated Poor. For more information, see Section 8.5.5, Lost Data.

    Jitter Buffer loss

    Determines how datagrams lost due to jitter buffer overruns or underruns are mapped to VoIP quality ratings. If jitter is detected, jitter buffer loss becomes a MOS impairment. Set the maximum amount of jitter buffer loss, expressed as a percentage of all datagrams sent, that a call can have if its quality is rated Good or Acceptable. Any call with higher jitter buffer loss is then rated Poor. For more information, see Section 8.5.3, Jitter.

7.8.2 Working with Firewalls

If there is a firewall on your network, you need to ensure that simulated traffic, plus flows carrying assessment setup information and assessment results, are allowed through the firewall.

Running Windows XP Service Pack 2 or running Windows Server 2008 is equivalent to running with a firewall, so the steps detailed below apply to this configuration. For more information, see Windows XP Service Pack 2: Firewall Feature or Windows Server 2008: Firewall Feature.

Vivinet Assessor uses RTP, which is equivalent to UDP for many firewalls, for simulated VoIP call traffic, and uses TCP for setup and reporting. For more information, see Section 1.3, How Vivinet Assessor Works.

The extra configuration you do at the firewall depends on the type of firewall you are using and whether the firewall is located between the Vivinet Assessor Console and the , or between the endpoints in a call group.

From the Assess VoIP Quality view, click Assessment Options on the Options menu, and then click the Firewall tab. Use the information in the following topics to make sure your firewall and Console settings are in agreement.

NAT-Enabled Firewalls

Network Address Translation (NAT) can be disruptive in VoIP networks because the addresses the firewall needs to translate are hidden within the payload of each VoIP packet. One workaround is to use static NAT, which maps each IP address for points on the secure side of the firewall to its own static IP address on the public or non-secure side.

NOTE:If a device is performing dynamic NAT, or “overloading,” you cannot run VoIP Quality assessments through the firewall. With dynamic NAT, private and public addresses are not statically mapped. Protected nodes may be assigned IP addresses randomly, when they make a request to send data to a public node, or they may share the same public IP address but receive different port assignments dynamically. This routing technique is called overloading. For a VoIP Quality assessment, the endpoints used in call groups must maintain the same addresses throughout.

With a NAT device active between the endpoints in a call group, enter the IP address of the endpoint as the Network address when you create the endpoint. Then enter a NAT address—the IP address assigned to this endpoint for network address translation—in the NAT address field on the Create/Edit an Endpoint dialog box. The NAT address allows the endpoints to find each other through the firewall.

See Section 7.4.2, Creating an Endpoint for more information about creating endpoints where a NAT-enabled device is active. Then consult Section 7.12.5, Performing Assessments with NAT.

If the NAT-enabled firewall is located between the Console and the , continue reading in the All Firewalls topic for more information about the necessary configuration. Then consult Section 7.4.2, Creating an Endpoint.

All Firewalls

The Firewall tab lets you configure a Reporting Port and a Call Traffic Port range. Reporting refers to TCP communications, setup and reporting information, between the Console and the endpoints Call Traffic refers to bi-directional endpoint-to-endpoint VoIP traffic using RTP, recognized as UDP by many firewalls.

NOTE:A NAT-enabled firewall requires special configuration when you create the endpoints in the Design view. For more information, see Section 7.4.2, Creating an Endpoint.

The necessary firewall and Console configuration depends on the location of the firewall in your network:

Location

Configuration

Firewall located between Console and

First, your firewall needs to be configured to pass TCP streams from the Console through Port 10115 to the , and from the endpoints to the Console through Port 10116.

On the Firewall tab, enter a Reporting port for the endpoints to use when reporting results back to the Console, or leave the default at 10116. Choose AUTO to let the Console choose the port dynamically; this means you will not know which ports to open at the firewall.

NOTE:After you set or change the reporting port, you must stop and restart the Vivinet Assessor Scheduler service. For more information, see Section 11.3, Scheduler Errors.

Firewall located between the

First, your firewall needs to be configured to pass bi-directional VoIP (RTP) streams through one particular range of ports. And it also needs to pass bi-directional TCP and UDP streams through Port 10115 because the endpoints need to be able to send setup and clock-synchronization messages to each other through the firewall.

On the Firewall tab, enter as the Call Traffic port the range of ports you configured at the firewall for VoIP RTP (UDP) flows between the endpoints Within any range of ports you set, the endpoints will only use even-numbered ports (which is what real VoIP RTP streams use). The default Call Traffic setting, AUTO, lets the endpoints choose the port dynamically. For VoIP traffic, they use even-numbered ports between 16384 and 65534.

Windows XP Service Pack 2: Firewall Feature

If you are running Vivinet Assessor on Microsoft Windows XP, Service Pack 2, you are running with a firewall and may find that assessments of VoIP Quality do not run properly. You must perform one of the following tasks:

  • Disable the firewall option in the service pack.

  • Configure the firewall to allow the ports and protocols listed in Section 7.8.2, Working with Firewalls.

  • Grant firewall access to the endpoint program.

To access the firewall feature in Windows XP Service Pack 2:

  1. Navigate to the Control Panel and double-click Windows Firewall.

  2. Click the Exceptions tab, which provides options for disabling or configuring the firewall feature in the service pack.

  3. To add the endpoint program to the list of applications that are allowed to send data through the firewall, browse for the endpoint.exe file in the C:\Program Files\NetIQ\Endpoint folder.

  4. Click OK, and then click OK again.

Windows Server 2008: Firewall Feature

If you are running Vivinet Assessor on Microsoft Windows Server 2008 or later, you are running with a firewall and may find that assessments of VoIP Quality do not run properly. You must perform one of the following tasks:

  • Disable the firewall option in Windows Server 2008.

  • Create two inbound rules for the following Assessor executables: Varun.exe and Vassessor.exe

To create inbound rules for Assessor executables:

  1. Navigate to Administrative Tools in the Control Panel and click Windows Firewall with Advanced Security.

  2. Select Inbound Rules and New Rule.

  3. Click Next.

  4. Click Browse and navigate to varun.exe in the file system.

  5. Click Next.

  6. Click Next.

  7. Click Next.

  8. Provide a Name for the rule, such as Allow Varun.exe.

  9. Click Finish.

  10. Repeat this process for Vassessor.exe.

7.8.3 Configuring Stop-Assessment Thresholds

A stop-assessment threshold allows the VoIP Quality Assessment to stop sending simulated VoIP traffic over your network if call performance is consistently poor. In the event of a prolonged network outage or extraordinary congestion, the Assessor Scheduler service will stop an assessment from adding its simulated traffic to the mix. By default, no stop-assessment threshold is configured for a new assessment.

From the Assess VoIP Quality view, click Assessment Options on the Options tab, and then click the Stop-Assessment Threshold tab to select the conditions that determine when Vivinet Assessor automatically stops a running assessment.

A stop-assessment threshold does not stop an assessment immediately. As the assessment runs, results from each set of simulated calls are checked as soon as the set is completed. The Scheduler checks the percentage of results that indicate Poor call quality or show that a call group or endpoint was Unavailable. It will not start the next set of calls if results exceeded your threshold. For example, if you configure your stop-assessment threshold to stop after collecting 25% Poor and Unavailable results in 3 consecutive sets of calls, the stop-assessment threshold kicks in if the Scheduler detects that the percentage or Poor and Unavailable results was 26% or higher during three consecutive calling intervals.

In the Run view, the status of an assessment that has been stopped by a stop-assessment threshold will read, “Assessment stopped by Scheduler. Threshold exceeded.” For more information, see Section 2.2.4, Vivinet Assessor Scheduler Service.

7.8.4 Setting Assessment Run Options

When assessing VoIP Quality, Vivinet Assessor runs simulated VoIP calls between the endpoints you selected for your call groups in the Design view. To measure the performance of these simulated calls, the endpoints generate timing records containing performance data and periodically send these records in batches back to the Vivinet Assessor, which uses them to calculate the metrics shown in reports and in Analysis Console for each call group. By default, a new timing record is produced every five seconds.

You can change two default settings that control how measurements are taken and reported during the VoIP Quality assessment.

To change run options:

  1. From the Assess VoIP Quality view, click Assessment Options on the Options menu, and then click the Run Options tab.

  2. To set the run option, select Override timing record duration and enter a new value. Accepted values are 1-60 seconds, inclusive.

    Some caveats apply, however. No timing records should be returned while simulated calls are running on the network because the batch file transfer traffic interferes with call performance and skews results. The five-second default avoids this situation, particularly if you also accepted the default options for the call traffic on the Schedule view tab. Calls that last one minute are sent between the endpoints every 15 minutes.

    If you try to set a timing record duration that will send timing record batches while calls are running, you will see a warning message.

    It is also important to ensure the assessment does not return too many results. The smaller the timing record size you select, the more records must be stored in the database. That is why five seconds is the recommended setting. If you select a setting that may return more than 3.6 million results for the VoIP Quality assessment, you will see a warning message.

  3. To see more detailed assessment results in Analysis Console, select Collect call details (timing records) when running a series of calls. This option affects the level of granularity of the data you collect. When this box is checked, the VoIP Quality assessment collects and stores individual timing records for an assessment in which you run a series of calls.

    When timing records are not collected for series of calls, results per call direction, per call group are totaled and stored in the assessment database instead.

    Timing records are always collected and stored when you run a single set of calls. When you create a new assessment, timing records are collected by default. For assessments created with an older version of Vivinet Assessor and upgraded to the current format, timing records are not collected by default.

For more information about timing records and how they are used in Analysis Console, see Section 9.4.2, Understanding Data Streams.