End-to-end Application and Voice Quality Testing

Previously, I discussed the first step in end-to-end testing: look at your infrastructure. Let’s take a look at what to do after testing the infrastructure: application and voice quality testing.

The basic procedure is accomplished by automating actual calls into the voice application server in a controlled manner and measuring the results at every stage. Isolating performance issues at the tested layer enables you to more easily discover the source of issues.

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Work Through a Variety of Test Cycles

Every layer of the pre-production environment should be put through a series of test cycles in order to ensure that everything is working correctly.

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First, perform a low volume functional test to assure that all contact center network elements are working as expected in the steady state. These test results can be used as a baseline to validate other types of behavior and traffic.

Next, steadily increase the test call volume in order to identify at what level of stress a problem – such as low PSTN capacity – might occur.

Following this test, stress the system at maximum capacity for a limited period in order to reveal issues that might occur during peak customer interaction periods.

Finally, stress the system at maximum voice and data volume for an extended period to uncover any memory leaks or problems with resource allocation.

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What Tests to Perform?

Voice should be looked at as an application among many running on an application server or PBX. Look closely at features within this application set such as:

  • Voicemail verification
  • Greeting verification
  • Queue treatment
  • Trunk verification
  • Answering endpoints
  • Bi-directional voice quality
  • Call recording
  • Capacity verification

Key Validation Points

Some suggested validations points to look at are:

  • Peak volume of calls placed through infrastructure
  • Dropped calls
  • Routing verification
  • Caller and agent voice quality throughout the application
  • Testing of the core to expected end game peak prior to individual site rollout

Voice Application Testing Use Case

Here’s an example of where voice application testing really proved beneficial. A large financial services company was seeing an increase in abandoned calls in the IP PBX, even when agents were available to take calls. Empirix performed a load test that was designed to push the IP PBX to the peak load of 10,500 concurrent calls with 7,000 agents.

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During the testing, once we got above 7,000 concurrent calls into the system, the abandon rates did increase significantly. At the same time, the IP PBX was reporting port network blockages. By listening to the recorded calls, we determined that callers were hearing more than 30 seconds of silence after the greeting message and callers from the test system then hung up.

The root cause was based on the way the customer had decided the application flowed. Additional VAL boards were needed to support the messages required, so callers would not hear such prolonged silence.

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