How to Ensure Your UC Services give Crystal-clear Voice Experience at Busy Hour when Reaching Full Capacity

 In Troubleshooting and Performance Monitoring
Reading Time: 5 minutes

The world’s call centers are the intersection between business and consumer.

These call centers process millions of calls each day, and they fluctuate for any variety of reasons. For example, call rates of five times normal busy hours during the start of an open enrollment for health insurance renewal are typical. Call centers are complicated systems functioning 24×7 and are vital to the growth and loyalty of the customer base. These organizations are determined to maximize customer service level and experience by:

  • lessening the time spent in a line waiting to get their calls connected to the agent widely known as ASA – Average Speed of Answer
  • reducing calls being ended while customers wait in the queue (known as Abandon rate), improving voice clarity and quality
  • eliminating dropped calls

Load testing follows the behavior of large volumes of clients using the call center (screen sharing, web activity, texting, voice & video calls, and emails) utilizing carefully tuned tools. These load testers stress your complete call center infrastructure in cloud, private or public or on-prem up to and beyond future expected traffic volumes, revealing the user experience you will deliver at busy hours compared to that you desire for your customers.

What Is Load Testing?

Load testing systems stress a complex telephony environment – signaling engines, policy algorithms, sophisticated call routing, database interactions, transcoding, Encryption and decryption subsystems, Public Switched Telephone Network (PSTN) access, network bandwidth and the virtual compute resources these apps may use. R/T Load testing finds the limits of your provision infrastructure by launching real VoIP calls, not simulated VoIP packets, from inside your private or public data center to exercise the IVR application, the softswitch, recording sub-system, ECB & SBC infrastructure behind the IVR.

The transcoder is the most fragile part of the telephony system in terms of complexity of the algorithms implemented. Audio distortions can occur in voice and video codecs and also when sending voice through a network device such as a transcoder (for example when transcoding G.711 to G.729) inside a Session Border Controller, SBC. Transcoders traditionally used dedicated digital signaling processor resources specifically designed for this purpose of processing voice and video signals. However, for most software implementations of telephony networks such as in softswitches, or most VM environments this task needs to be completed with general purpose computing. When this digital signaling processor DSP function in an SBC becomes congested audio impairments will occur. It is therefore essential to stress this sub-system to ensure good speech quality throughout the telephony network.

Load testing as a service Allows you to get your results and answers without investing in large scale equipment or lab facilities.

Load Testing of Real Time Applications Best Practice

Best practice is to generate RTP media belonging to the calls placed by the SIP signaling, steadily increasing the volume up to about 90% of the limits of the system. This we call background load generation. Then generate Real SIP calls with media containing real audio. On this top remaining 10% of capacity, that we call foreground traffic, we perform PESQ MOS i.e. Audio MOS measurements. Measurements of the performance of the Load test permit you to confirm that the entire telephony system end-to-end works as expected, and that computing allocation, CPU, memory, storage and networking are correct for your anticipated maximum load at busy hours. This ensures your user experience e.g. ASA, abandon rate etc. stays within required ranges and network capacity is proven to support bursts above expected volumes.

Understanding Cloud Load Testing

Cloud computing transformed how applications are deployed in an elastic environment, using only the computer they need at the time, being universally available and conveniently utilized by end-users and being maintained and updated incrementally & continuously. However, real time resources as used for VoIP and video conferencing require the application to be pinned to compute resources even virtual, even for cloud. They need to be there every millisecond of the day and regardless of how quickly applications can be moved to larger virtual CPU, this is never quick enough for real-time applications. Accordingly, load testing of the allocated compute infrastructure is vital.

Load Testing as a Service allows us to instantly bring the power of load testing services to a data center near you when you need it for specific test events.

Load Testing as a Service decreases the time and cost significantly to a point where load testing can be routine so that resources can be correctly engineered prior to deployment in operations, thereby reducing the costs of service support. Problems found during operations, during busy hours, especially intermittent problems, are the most expensive to isolate and fix. Problems resolved ahead of time are done so at about 1/10 of the cost. Load testing helps ensure critical scalability of applications such as real-time voice/UC as cloud services.

Load Testing of Cloud-Based Session Border Controllers (SBC) and Softswitch (HPBX)

Here are some aspects of SBC and softswitch infrastructure which benefit from load testing, especially as Specific functions of an SBC and softswitch are moved to computing resources which are challenged by the algorithmic intensity of voice processing as we trend towards Network Functions Virtualization [NFV]:

  • Registration storms
  • Distributed Denial of Service attacks (DDoS)
  • Call Control Capacity verification
  • Performance under real-world adverse network conditions
  • Security – e.g. Failed registrations, unauthorized call attempts and fuzzed SIP messages
  • Transcoder performance delivering good Quality of experience (voice and video quality)
  • Invite and registration spoofs

These tests benefit companies by providing the insights into expected performance in the following areas:

  • Proper handling of spoofs and attacks
  • Video and voice quality not influenced during attacks
  • Effect of data load on voice quality
  • Peak volume of calls placed through the system
  • Accurate mapping of the numbers

The Secret Sauce


Teraquant load and functional tests, unlike the usual tools used to stress your network, actually register on your voice switch which allows us to load test your voice devices and infrastructure as well as, not just your network bandwidth and QoS.

Teraquant voice Load testing as a service produces VoIP with media packets in large volume creating background load. This loads the device-under-test or network under test to a certain level approaching full capacity. We then generate foreground traffic where the media packets contain real audio on which we do audio MOS or PESQ /POLQA MOS speech quality measurements which measures in detail whether the voice is suffering signaling processing corruption as it passes through the DSP transcoder.

Teraquant foreground tests check the quality across a narrowband to wideband transcoder, giving audio experience end-end. This is essential for environments such as Microsoft TEAMS to the PSTN where narrowband to wideband transcoding is typical.

Teraquant load and functional tests are also monitored by state-of-the-art Service Assurance, recording any faults in the network that would account for less than perfect performance and providing lasting graphical reports to archive for future reference.

If you would like to know how your real-time apps will perform in your new cloud environment at busy-hour for your entire call center, your staff and your customers, please get in touch now to learn more.

For more information, view:
Load and Stress Testing as a Service