We believe that VoIP and IP Telephony (IPT) have passed the "tipping point" so that the key question now is no longer whether/when to install, but how to manage what you have installed. So today we'd like to direct our readers to a continuation of a great tutorial series that discusses the myriad factors that affect VoIP call quality performance (e.g., MOS, latency, packet loss, jitter buffer loss and ACOM), and troubleshooting methods. 

The full tutorial, provided by NetQoS can be found here.

Once a call is connected successfully, you can begin an interactive conversation. Just as the speed of call setup affected your opinion of VoIP system performance, the audio quality of the conversation plays a key role in your perception of the overall user experience for the call. In the past, some phone companies advertised the fact that the quality of their calls was superior to that of other companies. But the differences among them were actually quite minor; in fact, we’ve become accustomed to the very high level of quality achieved through decades of innovation in the PSTN.

The PSTN took advantage of the fact that once a call was connected, the resources needed for that call were reserved for the duration of the conversation. In the world of VoIP, as calls are added to an IP-based network, the necessary resources are most often shared by all network users. Quality cannot be guaranteed and must be carefully managed from the network performance perspective to provide a high level of network QoS.

The rise of the cellular or mobile phone has somewhat prepared us for sub-PSTN call quality, but the reduced quality associated with cell phones comes with the significant advantage of mobility. For business communications, reduced call quality can have a direct impact on the bottom line. If you can’t talk to your business partners and customers, revenue will likely suffer. As more workers become mobile and need the capability of high-quality business communications wherever they may be, a new premium is being placed on VoIP call quality.

The quality of experience that you and your users have with the phone system is closely related to the perceived quality of each call. Call quality is not a completely objective measurement, and thus it is important to understand some of the different standards for voice quality and the methods used to evaluate it.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Larry Hettick is a principal analyst at Current Analysis.