What are factors that affect call quality?

There are three main factors that affect call quality.

1. Latency - The time it takes a voice packet to reach its destination. Latency of 150ms (thousandths of a second) is barely noticeable, however latency higher than 150ms adversely affects VoIP Quality of service.
2. Jitter - The arrival time of individual packets making their way along routes over the Internet. Jitter can be caused by Internet congestion, timing drift, or Internet route changes. Jitter greater than 50ms (thousandths of a second) can result in packet loss and degraded voice quality.
3. Packet Data Loss - Packets are sent over the Internet and reassembled at their destination. Packet loss is measured as a percentage of packets lost with respect to packets sent. Packet loss occurs when packets are dropped by network congestion. Less than 1% packet loss is considered “good” for audio and video.