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See explanations of the scores below.
Mean Opinion Score (MOS)
The MOS score is a measure from 1 (being the worst) to 5 (being the best). MOS is quite subjective, as it originated from the phone companies and used human input from related quality tests. A VoIP simulation that drops below 3.5 is considered poor quality, a measure of 4.2-4.5 is considered good quality.
Jitter or packet delay variation (PDV)* tested on this page
In VoIP, jitter is the variation in packet transit delays (from serialization, propagation, and buffering effects on the stream). Jitter is significant to real-time applictions because the receiver must dimension its jitter buffer based on maximum jitter, which adds delays for all packets and causes eventual loss when jitter values exceed buffer capacity.
Packet Loss* tested on this page
Packet loss occurs when one or more packets of data travelling across a network fail to reach their intended destination. Here it is measured as a percentage. Call quality deteriorates when this value exceeds 5%.
Bandwidth and Latency* test found here
Measured in bits transferred per second, bandwidth is the maximum throughput of a network. For VoIP, enough bandwidth must be supplied to allow for the transmission of voice data in real time. We recommend 100 kbps per simultaneous call. A good rule of thumb is to consider 1/10 of your organization is on the phone at any given time, or 100 kbps for every 10 employees.
Measured in milliseconds, latency measures the time it takes to move a VoIP packet from one point to another.