Posted by: paragon | November 24, 2006

Understanding VOIP – Key Elements to Understand

*** What is Jitter

Jitter is the variation in time between data packets sent and packets arriving caused by network difficulties such as route changes, congestion, packet loss, traffic regulators etc., and plays a major role in the quality of a VoIP call. Excessive jitter occurs when the time delay is too long (high latency) and packets arrive outside the time window and get lost from the call (discarded). As a result, the recomposed sound no longer reflects exactly what was sent, and depending of the extent of the delay may not be understandable by the recipient.

*** What is Packet Loss

Packet loss plays a key role in the quality of VoIP connections, as high packet loss causes some of the voice data not to arrive to the recipient. Packet loss occurs when voice packets are discarded by the jitter buffer, or dropped by network routers/switches due to high congestion. MyVoIPSpeed measures the percentage of packet loss and reports the associated level of sound quality.

*** What is QOS

Quality of Service (QoS) is a feature of routers and switches which prioritizes traffic so that more important traffic can pass first. The result is a performance improvement for critical network traffic. QoS equipment is useful with VoIP phones or in LANs with high volumes of local traffic. 

Also, QOS represents the level of consistent download bandwidth speed (or throughput) provided by your ISP. A consistent broadband speed results in a better quality connection for for time-sensitive applications such as VoIP or multimedia.

*** What is MOS

The MOS, or Mean Opinion Score, is a numeric measure of the sound quality at the receiving end of a communication circuit. Although the score is subjective it provides a widely-used method to rate the quality of voice communication in a simple way that meaningful to end users. The score is normally between 1 and 5 with 5 being the best.

The MOS value is reported in the Summary tab once a connection test completes, a VoIP simulation that drops below 3.5 is considered poor quality, a measure of 4.2-4.5 is considered good quality.

*** What is MOS

Max Pause is the longest pause recorded between data transfers during the download speed test. This should be a very small number. If not, it could indicate Internet congestion or a bad Internet connection.

The Maximum Download Pause and Average Download Pause values are reported in the Advanced tab once a connection test completes.

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