...to measure Quality of Service (QoS) parameters like jitter and packet loss, and it will provide an estimated MOS (MeanOpinion Score) to tell you how good the quality of your voice calls is likely to be." Complete Story Related Stories...
http://www.linuxtoday.com/news_story.php3?ltsn=2009-07-11-002-35-NW-NT
...Assessment? Organizations often underestimate the task of network assurance throughout the VoIP deployment life cycle. A meanopinion score [MOS] and a couple delay and loss measurements are not enough to judge call quality and network capability nor do...
http://www.apparentnetworks.com/uploadDocs/VoIP-White-Paper.pdf